House didn't know what drew him to Wilson's office that evening, after even the hardest working oncologists normally went home, but when he saw that the door was slightly ajar, he didn't hesitate to push it open.

"Don't turn on the light."

House's hand hovered in front of the light switch and then dropped. "Headache?" he asked. "Or hangover?"

"At night?" Wilson turned his head in House's direction, but there was only a sliver of early moonlight to illuminate his face.

House thought he saw something glimmer on his cheeks nonetheless. "Tell me you're not crying."

"I'm not crying," Wilson replied agreeably.

It didn't sound like he was crying, but House had never stuck around long enough on the rare occasions Wilson did cry to form a sense memory. But Wilson was standing in his office late at night with the lights off, staring out the balcony window, and in House's experience that wasn't usually a sign of happiness. Not that House had formed many sense memories of that either.

"Is there a rational reason why you're hiding here in the dark?"

"I'm watching the firefly."

It wasn't often that Wilson managed to surprise House, but he came close this time. "Firefly? Are you on something?" Flashes of light could be a neurological symptom. "There aren't any fireflies around here."

"They're the state insect of Pennsylvania," Wilson pointed out, his nose nearly pressed against the pane of glass as he peered out into the twilight.

"We're in New Jersey. On the fourth floor of a large building. Not the normal habitat."

"Maybe he didn't have a map. He's flickering by the miniature maple. See?" Wilson pointed to the ragtag collection of planters he'd started accumulating on the balcony since he'd moved into the hotel.

House stood next to him, even though it was probably just Wilson's imagination, or stray moonbeams striking a metal surface. But then he saw it, a jagged flash of light dancing and swooping around the dark silhouette of the tree. "How do you know it's a he?"

"The males flash first to attract a mate," Wilson replied. "I've been watching and waiting to see if there's an answer, but he's all alone. I guess he got lost somewhere along the way."

House was close enough to touch Wilson, but he was both attracted and repelled by the sadness in his voice. "Could be for the best," he said, drawing on his own dim memories of firefly lore. "Some female fireflies mimic another species' flashes to lure the males in and eat them. I've heard the Jersey variants are particularly tricky."

Wilson didn't smile, but the tension in his shoulders eased a bit. "Maybe he'll find his way home," he said hopefully.

"Or maybe he'll find a friend," House replied. He walked back to the door, but on his way out he paused briefly and flicked the light switch on and off in a pattern he hoped Wilson would recognize.