House sat at his desk Saturday afternoon, bouncing his thinking ball. Over and back, the pattern reassuring, the ball behaving as it should. He didn't notice Stacy's arrival at the office at first until she neatly darted through his line of fire between bounces and sat down in the visitor's chair. House caught the next bounce and returned the ball to its holder, then faced her. She again looked calm and collected on the surface but underneath even more tense than last week, and the faint whiff of smoke accompanied her again.

"I want to help you," he started, and Stacy flinched, reading his tone as, of course, she had had a lot of experience doing.

"But not with a sperm donation."

"No." He made that sound as firm and irrevocable of a decision as he could. She had to accept that fact before they went any further in this conversation.

"Don't you think you owe me this much from all our years together?"

He shook his head. "Nobody ever owes anybody a child, Stacy. Children aren't currency."

She winced at that shot. "I really do want one, Greg. I always have."

"I believe you," he replied. He did wonder if maybe the urge was stronger lately for either biological or relational reasons, as he and Jensen had hypothesized yesterday. But her voice was as unshakeable as his there, and while he might wonder about any additional motives, he couldn't question the fact. She did want a child, and he couldn't help sympathizing with her. Cuddy had gone through years of the lack, too. "But I can't do this, Stacy."

"Why not?"

He started counting out reasons on his fingers. "One, I could never just be a sperm donor and stand back, watching from a distance while my child was with someone else and didn't even know me." Unexpectedly, a wave of sympathy for the old man swept through him. Over 50 years, all through House's childhood and almost all through his adulthood, Thomas had stood back and watched his son at a distance, never stepping in. House realized anew just how hard that would have been for a parent. He never could have held his distance from Abby and Rachel for five decades, even if he thought it was for their own good, even if it actually were in fact for their own good.

"Greg?" Stacy was puzzled, trying not to be hopeful but definitely sounding confused. "You drifted off on me. Are you reconsidering?"

"No." He firmly grounded himself in the present. Focus, House. "Second, I'm not sure of the effect that this might have on my relationship with my own family, Cuddy and the girls, and I don't want to introduce any new stress on them. Cuddy and I discussed this, of course. She agrees with me." Living with him was certainly stressful enough at times; he didn't need to be deliberately adding complications to his precious home life. "Third." He paused as he struck off the point on his middle finger, then looked up at her, wanting to do a full differential on her reaction. "You said that Mark agreed to this. What exactly did he agree to?"

Stacy's eyes fell away for a second before coming back to meet his, and House mentally added 1000 bonus points to Jensen's ample balance. He also was a bit annoyed that he hadn't caught that nuance himself last week. Stacy had bowled him over with her initial request, but shock was no excuse for dropping details in a differential. She also had wrapped things up very quickly and left, ostensibly to let him think about things, but she easily could have wanted to avoid giving him time for further questions right then. "Mark did agree to sperm donation," she started, but even in her tone, it was qualified.

House drove them relentlessly to the point. "With me? Does he know you were going to ask me? Does he know where you are right now or last week?"

"Not yet, but I would tell him. I didn't even know what you were going to say, Greg. No point in getting Mark upset if it isn't more than hypothetical."

"So, you do admit that it would get him upset? And when were you going to tell him? After you were pregnant? Down the road? Only if you absolutely had to or if he suspected watching the kid? You were hoping you wouldn't have to tell him at all, weren't you?" She was silent.

House sighed. "Stacy, there is no way, absolutely none, that I am going to have a child of mine growing up in the home of a man who resents him because he's worked out that the kid is actually the son of someone else he knows. Zero chance. We're not going there."

"But he did agree to sperm donation, Greg. He'd know the child wasn't his."

"He wouldn't know that it was mine, and no way am I risking him tripping over that knowledge on his own. He might take it out on the child." House shuddered, remembering countless episodes with John.

Stacy came to attention, watching him. "Is that why your father…"

He cut her off. "We are not going to dig into my past. But my father is Thomas Thornton. You met him the other week. John House was just Mom's husband, not that he deserved even that much."

Stacy's voice was softer now, trying to be reassuring. "Greg, Mark would never do anything to hurt a child. Never."

"Good, but he's never going to have the chance with mine. You weren't planning on telling him unless you thought he was working it out, were you?"

Her fingers dribbled on the desk, then stopped. "Maybe he wouldn't have worked it out."

House shook his head. "That's playing with fire, Stacy. For one thing, I want to show you something." He fished out his cell phone and pulled up the shot of his grandfather playing the piano. "Look at that."

She did so, smiling at first. "That's a wonderful picture. It's really…" Her voice trailed off, and she frowned in analysis.

"That's not me. That's my grandfather, Timothy Thornton. I'm a dead ringer for him. And this…" He took the phone back and dialed through a few more pictures. "This is my brother. My half-brother." She looked at the picture of Tim and Thomas on horseback. "The entire reason that I never met my brother is because the old man realized that John would put two and two together the minute he saw us side by side. Of course, John had already added up that equation, but Thomas didn't realize it. I've seen pictures going back a few more generations, too. There is definitely a genetic history here of very strong resemblance that crops out regularly. And…" He changed pictures again. "That's Abby. For a female version, she has it, too."

Stacy studied the picture of Abby the longest, then handed the phone back to him silently. He continued. "With my luck, you would wind up raising the spitting image of me, and Mark would work it out before the kid was a few years old. And letting him work it out, or when you start worrying that he might be working it out, is definitely the wrong time to tell him. Then you'd have the fact that you had hidden it in the first place to deal with, and that would make everything worse. There's no way to sneak me in from the side, Stacy. You would need to tell him from the beginning. But even if he knew from the git go, having the kid of your wife's ex being raised in your house right in front of you, knowing that you hadn't been able to hit a home run yourself and he had stepped in to pinch hit, could be tough to deal with. I can't see Mark taking that well."

Stacy looked down at her hands. "So, there's no chance here?"

"Not the way you want it, no. But, like I said, I would like to help you."

"Medically, you mean? I told you, we've both been worked up, Greg."

"But not all doctors are created equal. I'd be willing to look at the tests that were run on the two of you and see if anything was missed or if I could come up with further suggestions." He hesitated. "And while talking in person and being able to ask questions would be far better, if you want, I'd be willing to do just a chart consult with Mark. He doesn't have to talk to me, but he does have to know you're consulting me, and I'll be a lot more specific next time asking you questions; I shouldn't have missed that point last week." Self-annoyance colored his tone briefly.

"It was thorough, Greg. At least, it seemed to be." She paused herself on the last words, considering a point that she hadn't before. She did trust his medical knowledge. Maybe he could come up with something new.

"It's worth a try, Stacy. Maybe something could come out of it. And if you'd like me to get my team involved on the differential, we could use an alias."

She still didn't like that but was starting to wonder if there really was a chance medically. "I'll think about it."

"Couple of other things that don't even involve my participation, medically or otherwise. Of course, there's the adoption option." He dialed up another picture on his phone. "That's Rachel. She's ours now."

Stacy sighed. "I really wanted one of my own."

"I'm sorry," he said, taking a second to fight off the image of kissing Cuddy. Jensen had forever stained that phrase for him now, which still, of course, was a vast improvement over thinking about falling down the stairs of his childhood. "There are also places where you can adopt an embryo. For couples who can't conceive but where the woman can carry, you can get implanted. You can actually go through the pregnancy and birth yourself that way, even though it's technically someone else's child. It isn't cheap, but the process is out there."

She hit the limit much as he did at times on conversations. "I actually don't know whether…" She stood up abruptly. "I'll think about it, Greg, but I wish we could just use the easy way."

"It isn't the easy way, Stacy," he replied. "It wouldn't work."

She wasn't quite convinced, but at least she respected his resoluteness. She started for the door, then turned back just before she reached it. "Thank you for talking to me. I'll let you know if - if I want to again. And Greg, whoever your psychiatrist is, he's a good one."

"I know," he said, but she was already gone. House was left at his desk, looking at the picture of Rachel. He switched after a moment to the picture of the four of them and spent a long time looking at his family. "I'm sorry, Stacy," he said again to the empty walls of the office, and then he stood up and headed home.