It's still Christmas.

House sits in his favorite chair, strumming his guitar, trying to string together as many annoying yuletide carols as possible in an impromptu medley.

There is a loud knock at the door to his apartment.

"Go away!" House answers, and goes back to plucking.

The knock persists, messing with the musician's concentration. Heaving a sigh of irritation, House gets up to drive the intruder away.

As though reading his thoughts, the door bursts open and the intruder struts in as though arriving at a party where he is the guest of honor.

"Hello, Doctor," the familiar voice says.

"Oh dear God."

Standing tall and proud, garbed in a white hospital gown, is Kalvin Ryan, flamboyant photographer, HIV infectee, and, until his highly dramatic stint at PPTH, a carrier of equinococosis parasitic cysts.

"How the hell did you get into my apartment?" House wants to know.

"Relax, relax." Kalvin tries to make him comply with broad hand gestures. "Everything's going to be just fine."

House shifts his weight and grips his new metal cane. If this guy was crazy enough to break into his apartment, House could only imagine what else he was capable of. "Look, I don't wanna rain on your holiday parade, but I'm not in the mood for company tonight. So just be on your way and you won't have to meet my new friend." He waves the cane in the air. "He's considerably more ill-tempered than his older brother."

Kalvin's only response is a self-indulgent laugh. "Oh. You're so much funnier when I'm not depending on you for my life."

House cocks his head to the side, analyzing Kalvin from a different angle. "You seem lucid. What drugs has party-boy been popping tonight?"

"Honey, right now, I'm not the one with the drug problem." Kalvin points to something on the other side of the room.

House follows his finger and is boundlessly surprised to see . . . himself. His own body, wearing the same clothes he was wearing now, lying in a stupor on the apartment floor.

Kalvin giggles. "You see, Doctor House, tonight is different. Tonight, I don't need your help. You need my help."

The very idea brings a half-smile to the doctor's face. "I may be involved in a drug-induced hallucination right now. I may even be at a moral and spiritual low point in my life. But I've still got a long way to fall before I'm at a point where I need your help." House twirls his cane menacingly. "Now. Go away."

Kalvin laughs again. "My dear doctor, do you really think that you can hurt me with that?"

House shrugs. "Check the scoreboard. The Canes are 1-0. 2-0 if you count the time they knocked your dad out. If I were you, I'd wait til next season to try and make a comeback."

"Doctor House, you can't hurt me with your cane because I can't be hurt. I can't be hurt because I'm not tangible. I'm not tangible because I'm not Kalvin Ryan."

"Oh boy."

"Do you know who I am?"

"Let me guess. The Easter Bunny?"

"Funny. But, no." Kalvin spread his arms wide, and a strange white mist seemed to hang from the sleeves of his white hospital gown. "I am—the Ghost of Christmas Past." He finished with a bow and a flourish.

"Riiiiight."

Kalvin almost looked hurt. "You don't believe me?"

"Whether or not I believe you is irrelevant. Whether or not your statement is true is irrelevant. The only thing that's relevant is: you're not welcome here. This is my apartment. I don't care if you're the Ghost of Christmas Past, or Rudolph the Red-Nosed Reindeer, or an Angel of the Lord. You're annoying. Leave now or suffer the consequences."

"Okay. I'll leave. But only if you leave with me."

"I'm not going anywhere."

"What if I made it a little easier to get around?"

"Got a one-horse open sleigh parked out there?"

"Not exactly." With another annoying flourish, Kalvin—or the Ghost of Christmas Past—waved his hand and House's new cane slipped from his fingers.

The doctor bent to pick it up and felt something strange. Cautiously, he put a little more weight on his right—

And found himself standing on two legs.

Even stranger, he reached for the place where a big empty hole in his leg should be and found . . . a thigh muscle.

"Ooookay. I think I'm ready to give you the benefit of the doubt."

Kalvin grinned. "I knew you'd see it my way." He stretched out an arm. "Now, take my hand."

"I think that might be carrying it a bit too far."

"Oh, come on."

Experimentally, House extended an arm. But instead of grabbing Kalvin's hand, he swatted at it, and found that his arm passed through that of his former patient, as though nothing was there.

"Okay. Check on the being intangible thing."

Kalvin grinned. "Are you ready?"

"Do I have a choice?"