There was something wrong with Dean, Sam was sure of it.

At first it had seemed like Dean just had a mild hangover, which happened enough that Sam didn't worry about it. But then he had reacted like he didn't know Cas, and that was impossible. Even if something had gone wrong between them, which Sam highly doubted, Cas would have wiped Sam's memories as well. He was thorough like that. He would have just disappeared, he wouldn't have left Sam knowing and Dean clueless.

Then there was the lack of excitement over the pie. Dean would have snatched it at the first opportunity, but this morning he had politely taken a slice, even looking mildly confused as to why eating pie with breakfast was an okay thing to do.

After breakfast, Sam went to get his suit on and told Dean to do the same and grab his FBI badge, since he seemed in need of reminding. Sam made sure to grab the Demon knife and the Colt, since he didn't trust Dean to remember them. Or use them correctly, for that matter. Really, Sam just hoped Cas would show up again and help make sense of this.

When they were ready to leave, Sam grabbed the keys to the Impala, trying to gauge Dean's reaction. Or lack thereof. Dean didn't react in the slightest to Sam just assuming he could drive.

On the way into town, Sam turned possibilities over in his mind. Dean had the anti-possession tattoo, so he wasn't a Demon. There hadn't been signs of a struggle in the motel room, so it was unlikely Dean had been attacked by anything. Besides, Cas had been there with him at least most of the night, and if something had gone wrong, he would have come to Sam first.

So Dean was just...different? It didn't add up. And Sam had enough experience with things that didn't add up to know that something was very, very wrong.

When they got to the scene, the local law enforcement had the place taped off. The attack had happened a day ago, but the house was still a crime scene for the time being. There was an officer stationed by the front door.

Sam led the way up the steps, Dean following nervously behind him. "Ghost sickness, maybe?" Sam thought when he caught a glimpse of the uncertain look on Dean's face. "No, that doesn't make sense."

"Good morning officer," Sam said when they reached the officer at the door. "I'm Agent Nichols, this is Agent Peters." Here he held up his badge, as he always did. Dean was a little slow on the uptake, and still didn't seem sure of himself.

The officer seemed to notice this and raised an eyebrow curiously. "What's the problem son?"

"Excuse my partner, he's new," Sam said, casting a glance at his brother and replacing his badge. "We were sent in to check things out."

"Why's that?" the officer asked.

"We think there might be a connection to another case we've been working," Sam explained.

"You think it's a serial killer?"

"Yeah, something like that," Sam said noncommittally. He nodded toward the door. "May we?"

"Yeah, sure," the officer said, opening the door for them. "If it is a serial killer though, he's a weird son of a bitch."

"That so?" Sam asked.

The officer nodded and shut the door behind them.

"Alright," Sam said. "The report said he was found in the bedroom. Upstairs." He started to head up and noticed Dean wasn't following him. "Dean?"

"Yeah," Dean said, looking up at him. He seemed distracted. "You go on ahead, I thought I saw something."

"Dean," Sam said, annoyed. Dean didn't seem to hear him, and walked to the back of the house. Sam rolled his eyes and continued upstairs.

"Al, where have you been?" Dean (or rather, Sam Beckett in Dean's body) asked, exasperated, as he approached his holographic friend.

"Sorry, I went to check on the guy," Al said, not elaborating.

"Where am I? And who is this guy?"

"You're in a small town in Oklahoma. There have been a few weird deaths in the last few months," Al said, reading off of Ziggy's screen.

"Yeah, I gathered that part," Beckett said. "Apparently we're here to investigate one, but I don't know Al. These guys use fake badges and have more guns than I've ever seen in one place outside a range. This guy, this Dean guy I'm in, he sleeps with a knife under his pillow."

Al furrowed his brow. "Well that's a little weird. But Ziggy says they help people, so it must come with the territory."

"What does Ziggy say I need to do to get out of here?" Beckett asked, annoyed and slightly frightened. This was helping people?

"I'm right here you know," Ziggy said, sounding miffed.

"Fine, Ziggy. What do I need to do?"

"I'm not sure yet, but you don't need to speak as if I'm not here."

Beckett pinched the bridge of his nose. "Alright, so I'm just supposed to go along with this?"

"For now, yeah. It's what you've always done," Al said.

"I don't know that I can do this though," Beckett said. "This is way out of the realm of anything I've done."

"Dean?" Sam asked, brow furrowed, as he descended the steps.

"Over here," Beckett said.

Sam walked over to him. "Did you find anything?"

"Wha-No. Must have been a trick of the light," Beckett said as Al said his good luck before stepping through his door and back to his own time.

"Good, because I think you should go have a look at what's up there," Sam said.

"Oh? You think you missed something?"

Sam frowned. "No. But I think you need to get up there and take a look."

"Yeah, sure," Beckett said, heading to the stairs.

Sam watched him go and sighed. He looked up and shook his head. "Alright Cas, I don't know where you ended up, but I need you to come back here. Something's really wrong with Dean. I'm on the first floor of the house at 472 Main Street in a town fifty miles west of Oklahoma City."

There was a flutter of wings and suddenly Cas was there. "What's wrong with Dean?" he asked immediately, his face worried.

"I don't know," Sam said. "He looks like Dean, and he sounds like Dean, but he isn't. I don't know what it is. Was he okay last night?"

"He was normal," Cas said. "I had to leave early. Without Michael, there's fighting within Heaven, and I needed to go make sure the others weren't killing each other. Dean was fine when I left."

"When did you leave?"

"Two or three, I think."

"So sometime between then and when I got back at around eight, something happened to him," Sam said.

"Was there anything off about the room?" Cas asked, his face serious.

"Nothing," Sam said, exasperated. "There was nothing out of place. Just Dean."

There were footsteps on the stairs again, and Dean's voice saying, "Yeah, you're right, that's weird."

Cas immediately stiffened. "That's not Dean," he said.

"Yeah Cas, I know," Sam said. "Dean and I already had a theory going in."

"No," Cas said, voice firm. "That doesn't even sound like him."

Dean entered the room and Cas immediately had his angel blade out.

"Who's this?" Dean asked, brow furrowed.

Cas looked like he was about to lunge at Dean, but Sam held him back. "Cas, don't."

Cas turned and glared at Sam. "How did you not recognize that this isn't Dean from the very beginning?"

Dean looked shocked, but it was Sam who said, "Cas, I don't know what you're talking about. He looks like Dean."

"You can see me?" Dean asked Cas.

Cas turned his glare on Dean. "Who are you?" he demanded.

Dean looked between Sam and Cas and sighed. "Well this is a new development. I've almost never had to explain this to anyone," he paused. "It's a little weird."

"Try me," Cas said.

Dean didn't like the murderous look this Cas person was giving him, but he continued. "My name is Dr. Samuel Beckett. I'm a quantum physicist. I developed Project Quantum Leap to explore time travel. I stepped into the machine, and I've been leaping between people ever since."

There was a pause while Beckett let this sink in.

"Time travel?" Sam asked.

Beckett nodded. "I take over a person in a certain time period, to change things that went wrong before. When whatever it is is put right, I leap out and go to someone else."

"Where is Dean?" Cas demanded.

"He's in the waiting room at Project Quantum Leap," Beckett said. "He's safe," he added quickly, seeing the looks Sam and Cas gave him. "He stays there only as long as I'm in his life. When I finish what I need to do, I'll leave and he'll be back."

"And what do you need to do?" Sam asked.

"Ziggy isn't sure. She's a parallel hybrid computer. And her ego is the size of this house. But she knows what happened here the first time, and she lets me know the course of action that is most likely to get me to leap."

"So...? What happened the first time?" Sam wondered.

"I don't know. Al hasn't told me," Beckett said.

"Who's Al?" Cas asked.

"My friend. He keeps an eye on the whole project. He can appear to me and help me figure out what's going on."

As if on cue, Beckett saw Al step back through his door, saying, "Sam, I think Ziggy might be on to something."

"Who are you?" Cas asked, watching Al appear out of thin air.

Al looked up, his eyebrows raised in surprise. He looked at Cas and then to Beckett. "This one can see me," he said.

"Of course I can see you," Cas said. "Don't be ridiculous."

"Cas, who are you talking to?" Sam asked, slightly concerned.

"What do you mean?" Cas asked, his brow furrowed in confusion. "He's right there."

"It's Al," Beckett explained. "He appears as a hologram, but it's tuned to my brainwaves. Usually I'm the only one who can see him."

"And there's never been an exception?" Sam said, not buying it.

"No there are," Beckett said. "Children, animals, and the mentally handicapped."

Sam snorted. "Well Cas is none of those things."

"Then how can he see me and Al?"

"I'm an Angel of the Lord," Cas said.

Beckett blinked at them for a moment. "Oh. Well, that's a new one," he said, scratching his head.

"Yes it is," Al said. "Anyway Sam, Ziggy thinks she knows why you're here."

"Great, tell me," Beckett said.

"Okay, I don't like this," Sam said. "Where the hell is he?"

Cas sighed and pressed his first two fingers to Sam's forehead. Sam felt a rush of energy, and suddenly there was a old man standing there with them. And Dean didn't look like Dean, but like a middle aged guy with a grey streak in his hair. "Better?" Cas asked.

"Yeah, I guess," Sam said, surprised.

Cas looked up at the door and vanished just as it opened.

"You almost done in here?" the officer asked.

"Yeah, I think we're just about finished," Sam said, managing to still sound professional. "Just another minute."

The officer nodded and closed the door again.

Cas reappeared, eyeing the door as if to make sure it was going to stay shut. "I think it'd be better if we continued this conversation elsewhere."

"Probably," Sam said. "Doc here and I will meet you back at the motel."

Cas nodded and vanished again. Al said something about being back in half an hour and stepped back through his door.

Beckett stared at the empty space. "So he's actually an Angel?" he asked.

"Yeah," Sam said, clapping a hand on the other man's shoulder and turning him toward the door.

Meanwhile, back at Project Quantum Leap, Dean was pacing the waiting room. He couldn't stop moving. Something bad was going to happen. That Al guy had said so. Except this Doctor guy was supposed to stop it. But if he was supposed to stop bad things that had happened before, how was he supposed to stop it? If Dean hadn't been able to stop it, how was some guy without any experience doing this supposed to stop it?

The tumblers turned over in the lock and the door opened. It was Al, a tray of food and water in his hand.

"Thought you'd be hungry," he said, setting the tray on the cot.

"I'm fine," Dean said, not stopping his pacing.

Al watched him for a moment before saying, "I saw your friends."

Dean immediately stopped and looked Al dead in the eye. "My brother. Is he okay?"

"He's the tall one?" Al asked. Dean nodded. "Yeah, he's fine."

"And my..." Dean struggled for a word. "Cas, is he okay?"

"In the trench coat? He's fine too."

Dean felt a bit of tension leave him. "Good."

There was another silence between them. "That Cas, is he really an Angel?" Al finally asked.

"Yes," Dean said. "And that hunt you pulled me out of? We were going after what looked like a werewolf. Probably a pack. And we had one day left in the cycle to catch them as werewolves before we would have to wait another month. If your guy screws up, a lot of people are going to get hurt."

Al nodded, rubbing the back of his neck. He wasn't sure what to make of that. "Well, he's there because someone did get hurt. And Ziggy thinks she knows who it was."

"Ziggy? Who the hell is Ziggy?"

"She's our super computer. She knows what happened back on that...hunt? That's what you called it?"

"How? We cover our tracks."

Al shrugged. "She just knows."

Dean sat heavily in the chair. "Who got hurt?" he finally asked.

Al hesitated, seemed to debate lying. He sighed, figuring it would be better to just say it. "Sam Winchester. Your brother. He gets hurt."

"What?" Dean was immediately on his feet again, tears starting to fill his eyes. "You have to put me back. I can't lose him again."

"I can't put you back," Al said. "I'm sorry."

Dean scrubbed at his eyes. "What happened?"

"Ziggy says he was overpowered the first time. It turned him into a monster."

Dean turned his back on Al. Sammy? A werewolf? How had he let that happen?

"Hey now, my friend Sam is there. He'll set it right. He always does," Al said, trying to comfort Dean.

"No offense," Dean said, half-turning around, "but if I couldn't stop it, and Sammy couldn't stop it, and Cas couldn't stop it, then your guy doesn't have a prayer. And he needs to find a way to get out of my body. If anyone's going to be there with Sammy when this happens, it's going to be me."