When Karen returned to the University of Colorado's Old Main Building on Monday morning she was walking with Wen. They stood together outside the historic building before the history fellow went in and Wen left for his summer job in the library's computer lab.

The slender mathematician grinned playfully at his new girlfriend. "So, you're gonna spend the day with another man?"

Karen laughed sensually and kissed Wen on the cheek. "The ghost of anybody, even the excellent-looking Hannibal Heyes, is nobody to worry you, sweetie. And the Sumerian guys I write about have been gone even longer. See you at lunch!"

Yet when Karen got up the steep, marble steps of Old Main and into her office, she looked around a bit shyly at the Victorian wood moldings and other historic details of the office. Was the ghost of Professor Heyes in residence today?

If so, there was no sign of him. The sun shone cheerfully in the big double-hung window so brightly Karen had to lower the shade. She felt alone with her papers, books, and laptop computer. Soon, she was busily outlining a new dissertation chapter and lining up her sources. She piled articles and books on the desk.

She reached for a book on nineteenth-century archaeological digs in Sumer. She froze in surprise as she saw, next to the book she had reached for, the dark old leather binding of the book she had given to the heritage center the week before. It was the book on practical mathematics signed to Hannibal Heyes in 1891 by his mentor from Columbia University, Professor Charles Homer.

Who could have, or would have wanted, to bring the book back? Karen broke an informal rule of hers by stopping work on her dissertation before noon to do something unrelated to her academic work. She ran her hand along the thick wooden bannister as she climbed the stairs to the Heritage Center on the third floor with the book in her hand. She couldn't help thinking how Hannibal Heyes and his long dead students would have often climbed those same steps past the same elegantly turned newel posts and balusters, with the same spare brass chandeliers overhead.

"Karen, what's wrong?" Asked Mrs. Richards, the historian of the Heritage Center, in surprise when she saw the history fellow approach her desk. "You look as if you've seen a ghost. Gosh, you haven't actually seen him, have you?"

"No, but that antique mathematics text I brought up to you last week – I just found it back in my office. Here it is." She put in on Mrs. Richard's desk. "I promise, I didn't take it." Karen stated earnestly.

The university historian also looked taken aback as he opened the book and verified its identity. "Of course not. You couldn't have, unless Professor Heyes has been instructing you in opening locks. I put it in a secure cabinet." She stood and pointed to a room behind her desk. She unlocked the room and took Karen inside. There, among shelves and file cabinets, was a white metal cabinet with glass panels and a formidable-looking lock. The shelves were filled with rare books.

The historian said, "No one but me or one of the other employees here can open that cabinet. But good gracious, you can see the gap between books where the mathematics book was."

"Oh my God!" Exclaimed Karen. "Either you're playing a joke on me, or . . ."

Mrs. Richards looked extremely serious. "We may smile about our resident ghosts, Karen, but I do not mess around with historical artifacts. There are only a couple of us who can open this room or that cabinet. None of us would take anything out without telling the others or at least recording the move on the database."

"Is there a move recorded?"

Mrs. Richards shrugged. "I don't know. Let's go see." She went back to her desk, woke up the computer, and rapidly typed in some characters. "No, nothing recorded about that book since I logged it into the cabinet last week. I'm not totally sure how to log it back into the cabinet now, since it never officially left it. And who should we say moved it back to your office and when?"

"Mrs. Richards, you said it had been a long time since you saw that old math book. Where was it?" Asked Karen.

Mrs. Richards sat back in her chair, sighing. "I hate to admit it, I know it sounds nuts, but that book spent the last three years just where you found it. It was safe and sound - on the shelf in Professor Heyes' old office. The story from before I came was that every time anyone tried to put it in the library or to bring it here, it wound up back in his office. And there tended to be what I guess you would call hauntings – not ghost sightings but odd noises or other strange events - every time it was moved. We stopped being able to put professors or staff in that office. They wouldn't accept the assignment. So, when I arrived, I gave in to the stories. I left the book where it was. It's always stayed safe there. The hauntings stopped and we could use the office again. There used to be a plaque about Hannibal Heyes in that office, but we took it away to let the fuss die down. No one saw Professor Heyes again until you arrived."

Karen was startled. "Wait a minute - how did you know I saw him? Did Wen tell you?"

"Who's Wen?" Asked the senior historian.

"Winthrop Carter. He's a PhD mathematics student here. He's my boyfriend."

Mrs. Richards smiled. "Ah, that Wen. The cute boy with the blond ponytail. You work fast, Karen. Actually, Alice MacCall, the Fellowship coordinator, told me you thought you saw a man in your office. It wasn't hard to guess who it was."

"She didn't tell me . . ." Started Karen.

"Of course not. It was clear you didn't know about the office's history. She didn't want to scare you, or to make you think she was teasing you. We didn't want you to be uneasy in that office. But I suppose you want another space now." The older historian sounded resigned.

"Never! Professor Heyes feels very friendly to me. He doesn't bother me." Karen, knowing she was stretching the truth, looked down at the desk where she had placed the book. There was nothing there. "But Mrs. Richards – where did the book go?"

The senior historian's mouth opened and then closed. "He works fast, too, doesn't he?" The two historians laughed together. "As long as you keep it safe, you can keep it in your office, if that's where it went. Or maybe we should say, his office."

Karen was not that surprised to return to her office and see the familiar dark leather binding of the math book on a middle shelf, just where it had been earlier in the morning. She emailed Mrs. Richards that the book was safe back on its shelf.

But with her heart beating a little faster than normal, Karen looked up and said, to nobody who was visible, "Well, Professor Heyes, if you want your book by Professor Homer here, then it's fine with me. And it's fine with Mrs. Richards from the Heritage Center upstairs. But I do wish you'd help us to get your autobiography back from whoever stole it. Folks could learn from your book. I really want to read it."

When Karen met Wen for lunch at their favorite pizza place, she had quite a story for him. As they sat at a sidewalk café table under a red striped awning, she told her ghost story. He listened with keen interest between bites of pepperoni pizza and sips of coke. The cheerful Colorado sunshine seemed a long way from the gloom of traditional ghost stories.

"Wow!" Said the mathematics PhD student as Karen finished her unlikely tale. "Did anyone see Heyes carrying the book back to your - or his - office?"

Karen was silent for a moment. "Gosh, I didn't think of that. I didn't ask. We didn't see him take it from the desk in the Heritage Center, of course, because we were in the secure storage room when it vanished. Do you think someone might have seen his ghost walking down the hall with the book?"

Wen took up the debate with enthusiasm. "Maybe. Maybe they didn't even realize that guy with the book wasn't a regular 21st-century professor or something and didn't give him a second glance. Or maybe they might have seen the book floating down the hall? But you would have heard about that, whether or not you asked. So maybe it just materialized back in your office without crossing the space in between? Whatever happened, it sounds pretty fantastical."

Karen laughed uneasily.

Wen said, "But I will really wonder if the autobiography shows up after you asked for it. That would imply that Heyes actually knows you're here and heard what you said, and cared. I've always wondered if a ghost would really be present like a person and aware. I've heard about ghosts that were just like films playing over and over where something happened to them when they were alive – not aware of a living person there. Just going back through the motions. Like Marshall Fred White in Tombstone who hangs around where he was shot. I don't think he ever notices modern people who see him, even if they scream."

Karen shivered. "Oh, that sounds scary, whether or not the ghost notices. The living person would notice! I've heard of one famous and convincing ghost sighting from the ancient world – my period. Some British plumber during the 1950s was working up on a ladder in a really old rock cellar in York, England. He heard a loud trumpet and saw Roman soldiers in plumed helmets walking right out of the wall and past him. He was so scared, he fell off his ladder."

Wen had heard of this. "Yes, that's what I read when I was Googling ancient ghosts last night. He was terrified, which I sure understand, and tried to hide from the soldiers. But they weren't aware of him. They just marched right past, the way I guess they had done a couple of thousand years before. He said they looked as solid as living people. But he couldn't see their feet until they got into a trench - they were walking on the level of the ancient Roman road, which was more than a foot lower than the floor of the cellar. Historians thought the plumber's description of the soldiers' uniforms was wrong, but decades later they dug up arms and armor of local auxiliaries. They had different shields and stuff than the Roman regulars. The plumber had had every detail right."

Karen looked a bit pale. "That's not comforting at all, Wen. Having the soldiers not come after him might have helped the plumber some, but it still sounds really frightening. It makes me wonder if I might go to sit at my desk and find it already occupied! I guess if the ghost knew I was there, it might be worse."

"So, you've never run into a haunted Sumerian site?" Wen asked.

"No, never. The Sumerians themselves told lots of ghost stories. I used to wonder if I might see Sumerian ghosts on a dig, but I never did. And I never heard of anyone who had in modern times. I guess it was just too long ago for their vibrations or something. They were active about four to seven thousand years ago, long before the Roman soldiers the plumber saw. But the 1890s, when Heyes was here, - that's like yesterday for a ghost."

"So why are you so uneasy? You said Heyes seemed nice," said Wen.

"Yeah, nice, but also dead. Uncanny. If he showed up it would make me more than nervous!" Karen gave a shiver despite the summer heat.

Wen out his arm around he disconcerted young historian. "I'll keep you safe, honey. You want me to walk you back to your office and make sure there are no ghosts?"

"Well, since you offer, yeah. I would like that."

When they got back to her office, Karen noticed something sitting on top of the bookcase. It was well above her head, so she couldn't see more than the edge of something dark where it protruded over the front edge of the bookcase and even then, she had to stand well back. But she pointed it out to Wen. "Wen, that was not there before I went to lunch. I'm sure of it. Can you see what it is? Is it a book?"

Wen, who was much taller, craned his neck. "Yeah, it's a book alright. A big one. I can't see the title."

The eyes of both PhD students grew wide. They said almost at the same time. "Oh my God!"

Wen stood on Karen's chair while she steadied it. He took the large, heavy old book down carefully.

As he got the fat tome onto Karen's desk, Wen said, "Wow, there isn't any dust on it. The top of the book case is filthy, but the book is clean. If it had been there for even a few days, it would be dusty."

Wen handed the volume down to Karen. She put it on her desk. They could see the fancy gold lettering on the cover. It read, "The Autobiography of Hannibal Heyes and Kid Curry." The black leather cover was ornamented with embossed and colored pictures of two cowboy hats, two pistols, an opened safe, and a cactus. The colors were hardly faded by time. The two graduate students gasped.

Karen helped Wen down from his perch in her chair. The pair bent avidly over the handsome book. Karen's hands shook as she opened the cover. On the title page, it said the book had been written "by Doctor Hannibal Joshua Heyes in close consultation with his partner, Jedediah Curry." Just as they had suspected, it was signed and dedicated on the end paper in the author's firm, flowing hand. "To the students, staff, faculty, and alumni of the University of Colorado, with affection. Hannibal J. Heyes, PhD. August 25, 1916."

A shiver went down Karen's spine for about the third time that day. "Gosh, Wen, he heard me."

"And cared enough to pay attention. That's nice of him."

Karen took a deep breath. Then she said, "Thank you, Professor Heyes. We and Mrs. Richards will take very good care of your autobiography, and make sure the students here get to learn about you and your family."

Wen paused a moment, then added, "Yeah, thank you, Professor. My great-great-grand uncle was your friend Ev Carter. He was a great teacher. The family remembers him with pride." Karen was surprised to hear her brave boyfriend's voice shaking just a little as he finished his speech. She took his hand.

The pair climbed the steps to the heritage center, with Karen gripping their treasure to her chest.

"Look, Mrs. Richards! Wen and I found it in my office," said Karen, placing the volume on her desk. "I felt silly, but I asked Professor Heyes to help you find it, before I went to lunch. When I got back, there it was, on top of the bookcase.

"With no dust on it," added Wen. "So, it hadn't been there long. Hello, Mrs. Richards."

The Heritage Center's grey-haired historian already knew Karen's friend. "Hello, Wen. Why am I not surprised you and Karen would get to know each other?" Her eyes sparkled. Wen had spent a lot of time at the Heritage Center.

Wen smiled self-consciously. "She's pretty nice, and I guess Heyes agrees. We know where he found the math book he took back to his office. I wonder where he found his autobiography?"

"I suppose we'll never know," said Mrs. Anderson as she patted the cover affectionately. "It would sell for a pretty penny, being a signed first edition in nearly mint condition. Thank goodness, it's unharmed by its adventures. Maybe some used book seller just lost a prize bit of inventory sold to him by an impecunious and larcenous student. It's also a very interesting read. Heyes told wonderful stories, so perhaps some student or visitor just wanted it. Someone broke a glass case to get it. Professor Heyes would never have been so unsubtle. He had plenty of experience with more sophisticated way getting hold of things belonging to others. Though, of course, this actually belonged to him. Or to his school. So, he wasn't stealing to restore it to us."

Karen squeezed Wen's hand. "I hope he helps you to keep hold of it, this time, instead of taking it away as he did with his mentor's book. Can we come read it sometimes?"

"Of course! Thanks what it's for. I know the author would want you both to know what he and his partner had to say. And of course, you'll both be careful and stay in the Heritage Center. Just let me or whoever is at the desk know when you want the book and when you're done reading for the day."

Karen and Wen had lunch again the next day, this time at a local salad place.

"So, how's it going in the haunted office?" Wen asked as he put his paper napkin on his lap.

"Pretty quiet. At first, I kept wondering if he was watching me. If he is, he'll get bored in a hurry. Now I'm starting to settle in and get work done on my dissertation," said Karen. She stabbed at a cherry tomato, which escaped her fork. She stabbed again with more success. "How's your work going?"

"Oh, fine. No hauntings." He laughed. "I sure haven't told anybody else what's been going on with those books. They'd think we were nuts."

Karen sounded thoughtful. "Maybe we are. If Mrs. Richards weren't on board, I'd feel a lot sillier. She's a neat lady. Either she's playing an elaborate joke on us, or she's pretty cool with ghosts."

"And they are with her." Wen gazed at his lady friend. "And with you. I still haven't seen him."

Karen told Wen's hand. "Do you want to? See him, I mean. Could we try to go out to his house this weekend?"

The mathematics student said, "Sure. I don't have plans. Let me look into it. I know where Heyes Castle is, but it's not on any public road. I don't want to get you in trouble. But seriously, do you want to go out there to a spooky, empty old Victorian house? Considering what's already going on, we can't know what might happen."

"I'm game if you are. As long as you stay with me, I'll be good. I'm not saying I won't be scared, but you make me brave." Karen gave a Wen a quick kiss on the cheek.

"To tell you the truth, you make you brave, too, sweetie," said Wen. He kissed Karen on the lips, and not so quickly.

Both ghost hunters found a little time later that week to start reading the Autobiography of Hannibal Heyes and Kid Curry. But it was a long book and they were barely started. They didn't get past the childhood of the infamous pair.

Early Saturday morning, Wen and Karen pair drove in Karen's Jeep to a local stable just below the Flatirons. There were a few clouds scudding across the sky, but it didn't seriously look as if it would rain. It seemed a good day for a long ride. Wen's study of trail maps had revealed that a car could have gotten the pair most of the way to the old Heyes property faster than horses could. But a car would have left them stranded about five rugged miles from the lane that led to the old mansion. He couldn't see any access for cars except on private roads where they would not be welcome. But there were public trails open to horses. And seeing the countryside from horseback sounded appealing.

So, Wen and Karen got to the stable dressed in boots and jeans, with saddlebags full of water, lunch, maps, flashlights, and bug spray. They rented a pair of horses in western gear. "Thanks, Jim," said Wen to the man who ran the stable. "We'll get the horses back safely and before dark."

"You do that," laughed Jim, shaded from the bright sun by a ten-gallon hat. "You break 'em, you bought 'em. And those horses ain't cheap."

"Don't worry, Jim. We're both experienced trail riders," said Wen. "And we love horses."

The pair of ghost hunters walked their mounts on a trail through a dense pine woods, then trotted across a field. They stopped at the edge of a clearing. "You really are an experienced trail rider, right?" Wen asked Karen as he checked a map spread over his horse's withers. The calm creature was not frightened at all by the crinkling sounds of the map – he dropped his head to graze.

"As it happens, I am," said Karen, looking up from checking their location on her cell phone, "though more riding English than western. By the way, I've got only one line here. I think we're about to lose cell service entirely."

"No surprise there, with rock all around us. As long as I don't lose the trail map or drop my compass, we should be fine. There's the trail head going into the woods and up into the Flatirons. That should take us to the old Heyes estate lane, if we can stay on it in this rough country." Wen folded the map carefully, leaving their current location on top. He tucked it into a plastic bag and then into his saddle bag.

Then the rented horses, a pair of sturdy bays, were climbing the winding path on switchbacks through broken red brown rocks and dense pine woods. Wen and Karen rode with care, stopping often to rest the horses and make sure they were still on the right path. They climbed and climbed up rugged rocky paths. Then they descended into a green valley. Wen had to pull up his horse's head to keep him from browsing on the verdant undergrowth.

"Wow, look! Hannibal Heyes picked a beautiful place to build. It's like a mountain paradise," exclaimed Karen, patting her horse. "Wildflowers all over these hills."

"Yeah, and look at that waterfall up there running down that rock face!" said Wen. "And here's the path up to the house. We turn left here."

The path was rough, most of the gravel having vanished into the dirt with the years. It was too rutted for any vehicle without four wheel drive, but posed no serious problems to horses. Fortunately it hadn't rained recently, so there wasn't much mud. The setting was glorious, with dense green pines providing a dark background against which aspens shone. Snow touched rocky peaks in the distance towered against a brilliant blue sky.

"Oh, look, I see the top of a stone tower!" Exclaimed Karen. "See? It really is a Castle!"

Then they rode around a bend and came to a high chain link fence. The gate between two stone columns was secured with a massive padlock. A battered metal sign read, "Trespassers will be prosecuted."

"Rats!" spat Karen in disappointment. "But I'm no Hannibal Heyes. I won't break in just to see an empty house. We should have tried to contact the family before we came. Maybe they could let us in and show us around."

They rode up and down the high fence, but could see little of the stone house that was hidden behind trees well down the lane. The yard was too overgrown for them to be able to guess much about its appearance over a century before.

"It looks like we're stymied, at least for today," said Karen. "But somehow, I don't think Heyes and the Kid would want us to give up." She used the names Hannibal Heyes used in his book to refer to himself and his partner.

"Maybe. I don't know," said Wen. "But I think we should stop hunting their ghosts. Those guys were pretty good at avoiding pursuit when they were alive. You seem to have better luck when you just let it happen."

"So it seems," said Karen. She smiled at Wen. Things were certainly starting to happen with him.

They rode slowly in silence for a while, joining back up with the trail they had come in on. As they rounded a bend, Wen pointed ahead of them. Far in the distance, up a slope, they could barely glimpse two riders. One, in a black hat, rode a brown horse – could it be a claybank dun?; the other rider, in a brown hat, rode a black horse or perhaps it was a dark bay. As they got to a turn in the path, the two men in the distance urged their horses into a gallop that seemed reckless on so narrow and winding a mountain trail. Karen and Wen heard two faint, distant cowboy whoops. A shiver ran down both their spines. The riders vanished behind some pine trees high up the steep trail.

Karen whispered, "It can't be. It just can't be! It's just two guys."

Wen and Karen continued to ride at the walk, resisting the urge to gallop after the men they had seen. When they got to the part of the soft dirt path where the two men had been galloping minutes before, the two friends looked down. There were no hoof prints on the road, except the tracks of their own horses coming and going.

Karen laughed. "You think they're leading us on? Just giving us a glimpse like that and vanishing."

"Maybe," Wen laughed back. "Does seem like they don't want us to stop following." There was a brilliant smile on his face. "Both of them! Wow! Are you scared?"

"No," said Karen. "Or not much. Not with you here."