Out in the hallway, she sank to the floor, trembling. Her mind raced, and try as she might, she couldn't make any sense of all the thoughts and emotions flooding through her. She clapped a hand over her mouth as she began to sob. She wasn't even sure which emotions were the ones that made her cry; she just knew that she had to let them run their course for a while.

After a few minutes, she felt a little calmer. She went to the bathroom and splashed cold water on her face. As she stared at her reflection in the mirror, she had a conversation with her inner self.

Okay, Penny, what are you going to do now?

Sheldon needs my help. You know why he doesn't trust the others.

Oh, you mean the friends who call him an emotionless robot? The girlfriend who forms emotional attachments to her monkeys and then kills them and studies their brains under a microscope? Yeah, no surprise there...

Sheldon's... an alien. That's not even his real name. I can't... I can't deal with that. I don't know how to deal with that.

So don't. You're an actress. Take those feelings and put them in a box. You can deal with them later. Right now, Sheldon needs your help.

You're right. I can do this.

Penny formed a mental image of a cardboard box. She imagined placing all her panic and bewilderment inside the box, then she imagined firmly shutting up the box. For good measure, she taped it all around with packing tape.

There, feel better?

Sure, now I just have to deal with the fact that my best friend is dying.

You can do this, Penny. He trusts you. He needs you. Have faith.

That seemed to be the last thing her inner voice had to say to her, so she took a deep breath, squeezed her hands into fists and then relaxed them to release some of the tension she felt. She squared her shoulders and went back into Sheldon's room.

His gaze flew to her face the moment he heard the door knob turn.

"You're back," he murmured with a sigh of relief.

"Yeah, sweetie, I'm back." She sat down on the side of the bed again and held his hand in both of hers. She stroked the knobby protuberances along his skin and deliberately thought only of the man she knew as her friend.

"So, Sheldon, I know you well enough to know that you must have made some kind of plan. What do you need me to do?"

He gave her a faint smile. "Open my closet and look inside the third duffle bag on the floor. You should find a key with a large white tag attached. The key opens a unit in a nearby storage facility. I need you to go empty out the storage unit. There's not much there. Oh, and text Leonard. Tell him I have a cold and that you're going to go get me some soup or medicine. That will ensure that he doesn't return early."

Penny watched his face twitch with the usual tics as he asked her to lie for him. She wondered... no, she didn't wonder. That would mean opening that mental box that she knew she didn't have the capacity to handle right now.

"Will you be all right while I'm gone? I... I didn't even ask; are you... in pain? Can I bring you any painkillers or anything?"

"No, I'm not in pain, only weak... and drugs have always had unpredictable results with me." He laughed his breathy little laugh. Penny's heart caught in her throat as she remembered him racing around the apartment, high on caffeine and thinking he was the Flash. She swallowed painfully and looked away.

You can do this, Penny.

She got up and rummaged in the closet until she found the bag and the key Sheldon had indicated. There was no address on the label, just a number. Sheldon was too paranoid to write down the location of the storage facility, but he recited the address and had her repeat it until he was satisfied that she wouldn't forget.

She left his apartment in a daze. She drove to the storage facility, carefully thinking only about the traffic and the songs she was listening to on the radio. She found the right unit, a small outdoor space with a white roll-up metal door. The key fit in the large utilitarian padlock, although she had a hard time turning the key because the padlock seemed to be a bit rusty.

As she pushed up the door and stepped inside the darkened space, she blinked in surprise. The unit was empty. Just as she began to wonder what on earth she was going to tell Sheldon, she felt a faint prickling along her skin, and there was a low thrumming noise, so low it was almost felt rather than heard. She blinked, and suddenly there was a box sitting on the concrete floor in front of her. She bent down and touched it cautiously. It was just an ordinary cardboard box, large enough to be bulky and awkward to carry, but not heavy. She picked it up and placed it in the trunk of her car, which was parked just outside. On the drive home, she kept the radio turned off and thought about nothing.

When she returned to Sheldon, he instructed her to retrieve another one of the duffle bags from his closet. Pungent and exotic odors wafted up to tickle her nose as she opened the bag. It was full of amber glass jars and vials, along with a few cloth sacks and some tiny containers that looked like trinket boxes. They were marked with crinkly paper labels, handwritten in a number of languages.

"Holy crap on a cracker, Sheldon. What is all this stuff?"

He laughed his breathy laugh again. "When I began to give up hope that I would be able to mend my communicator, I spent a few years trying to find some substance that would counteract my blood poisoning. My colleagues thought I was suffering some kind of early mid-life crisis at the age of twenty. I even earned a master of arts in alternative medicine. Unfortunately, I was unsuccessful in finding a cure. However, through careful experimentation, I was able to identify a number of substances that had a salubrious effect. One of those ingredients will give me the energy I need to be able to make it down four flights of stairs to your car."

She found the bottle he described, a fat glass jar with something shriveled and gray inside. She helped him put a piece of it under his tongue and then wiped the gray powder off on her pajama pants with a grimace.

"The medicine should take effect in about a half-hour," he told her, and then hesitated. "Penny, I... I would appreciate it if someone were with me at the end. I always imagined that I would want to be alone to contemplate my life, but I am surprised to find I have somehow changed my mind."

She managed to crack a smile at that. There was the Sheldon she knew, surprised by the idea that he might actually want company. Then she remembered why he wanted her to be there, and her face fell.

"I will," she promised, biting her lip to keep from crying again. "I... I need you to tell me exactly what you want me to do."

He nodded, seeming able to move a bit more easily this time. Hopefully, the medicine or whatever-the-hell-it-was that he had taken was starting to work. He told her that they needed to go out into the desert, somewhere very remote. There were a few places he had selected and marked on a map in one of the duffle bags.

"So basically, we're going on a camping trip, except only one of us is coming back," she said with a little catch in her voice.

He hesitated, and then changed the subject. "I'm looking forward to going to the desert in more ways than one. It's always been so cold here on your world."

"Is that why you're always wearing a thermal T-shirt, even in the middle of summer?" Penny asked curiously.

He nodded shyly. "It's strange to be speaking of this so openly with you. In a way, I wish I had been able to do this years ago."

She looked away, blinking rapidly, and when she had her emotions under control, she looked back to him again.

He just looked at her with wide eyes, and then he carefully pushed himself into a sitting position, wincing as he did so, despite his claim that he wasn't in any pain. "I think I'll be able to walk downstairs soon. Please go pack your things now," he said.

She nodded, and crossed the landing to her apartment. She stopped for a moment in front of her door and stared at it. Had it really been just a few hours ago that she had blithely walked out that door, expecting to get soup for Sheldon and sing him "Soft Kitty"? She forced herself to extend her arm, to open the door and walk through it. In her bedroom, she blindly threw clothes, undergarments and toiletries into the large black duffle bag that Sheldon had given her. There had been an extra one, sitting empty on his closet floor, and she couldn't bring herself to ask if he had planned for this contingency, too.

It took only a few minutes to load up her trunk with the duffle bags—four now, with hers added to the pile. She took a deep breath, preparing herself for the next difficult part, getting Sheldon from his bedroom to her car parked on the street below.

Sheldon moved like an old man as she helped him down the stairs. His joints were stiff, and he leaned on her heavily, despite the drugs he had taken. A different substance, a viscous brown liquid, had restored his appearance. She gazed at him, thinking that he had always been so pale. How had she not noticed the blue undertones in his skin before? Maybe she had but never thought much of it.

By the time Sheldon reached her car and folded his long limbs into the passenger seat, he looked exhausted. Penny retrieved the map from the second duffle bag (she had hastily labeled them with post-it notes so she could tell them apart). Underneath the map was a thick envelope. Curious, Penny peeked inside and her eyes widened at the neat stack of crisp bills in different denominations. From the number of hundreds and fifties, she guessed there was more than a few thousand dollars. Bleakly, she wondered how well she really knew Sheldon, and how much of his life had been a lie.

She got behind the wheel and headed for Route 15, the freeway that would carry them east toward the desert. After a few miles, she glanced over at Sheldon. He was still awake, so she asked him curiously, "Aren't you going to tell me that my check engine light is on?"

He shook his head slowly. "It is irrelevant now. Before, my concern was of getting into a serious accident. I couldn't risk having my blood tested or undergoing any invasive medical procedures."

She stared straight ahead, fighting back the urge to cry, to yell at him. It was too much for her to process. She kept picturing the cardboard box image in her mind, imagined shoving all of her panic and helplessness inside.

They stopped once at a sporting goods store. Penny purchased an extra tent and sleeping bag for herself, along with several cases of water and a few other supplies. Sheldon had opted to remain in the car. After she had finished loading up her purchases, she got back behind the driver's seat. Glancing over at Sheldon, she commented warily, "You're turning blue again."

He nodded. "The pharmaceuticals I used to maintain my appearance are wearing off. They don't last long."

She frowned in confusion. "You couldn't have been taking that stuff every few hours your whole life."

"No, most of the compounds I use only enhance my body's natural abilities. The herb I used in the Arctic, for example, accelerated my metabolism. On my world, it would have been a prohibited substance, because it would have shortened my lifespan by decades. It didn't matter, though; they were decades I knew I would never see anyway if I didn't find a cure."

"Is that why you went to the Arctic? I always thought that you were really focused on the Nobel, but you said you couldn't attract attention by making any real scientific discoveries."

"Yes. There was a rare microbe that existed in sub-zero environments which I hoped to cultivate in an effort to purge the toxins from my blood. It was my last real hope, and one which I was reluctant to attempt because I knew the toll the expedition would take on my health. Ironically, it was the knowledge that my last-ditch effort to find a cure had failed that sent me into a deep depression, not Leonard's childish prank. I knew before I set out that my search for monopoles at the magnetic north pole would be unsuccessful. My people have known for centuries that monopoles aren't related to string theory in the way that I suggested."

They were silent for several minutes, and then Sheldon spoke again. "There's something you should know. In the third duffle bag is a round black device about ten centimeters in diameter... the size of a saucer," he clarified, seeing Penny's blank look. "It has four small depressions on its surface. It's another contingency. No one can see me like this. If we are discovered, I want you to hold the buttons for a count of five, and then you drop it and run. Understand?"

"What... what will it do?" Penny asked in a hoarse whisper.

A ghost of a smile flexed the corners of his mouth. "What I should have done when I first came here. It's a bomb of sorts, for lack of a better term. It will destroy anything in about a sixty meter radius. None of my equipment, none of my technology, can ever be discovered—or, to employ an over-used cliché—fall into the wrong hands. Press the buttons, count to five, and run."

Penny nodded and swallowed hard against the lump in her throat.