At the hospital, House wonders whether Boyd's tuberous sclerosis, while being a correct diagnosis, isn't as aggressive a case as they assumed. Maybe something else is making Boyd sick and causing all his symptoms, and they just happened to find something that explained it and went with that when it wasn't the answer. They need to look for something else. "It's lumbar-puncture time!" House declares.
But Boyd has seen this show before, and knows what to expect from lumbar punctures, so he doesn't want any part of them. He's sure that God will fix his problems. Foreman and Cameron appeal to Boyd's useless dad to step up and actually be an authority figure and make the right decision for his delirious, feverish son. Boyd begs his father to be strong in his faith and stuff, and the dad, looking kind of ashamed, refuses to let them do the lumbar puncture. "God knows the answer," says Dad.
So House calls upon Wilson to come back to Boyd and work his manipulating magic again. Wilson thinks they're better off slipping some antibiotics into Boyd's food and hoping that the drugs will combat whatever bacterial infection the kid has. Unless... "What if it's not an infection?" Wilson wonders. Maybe all the symptoms Boyd has, except the fever, are from his tuberous sclerosis, and the fever is just something unrelated that he picked up, maybe even at PPTH. Or maybe, House thinks, he didn't get it at PPTH, but gave it to someone at PPTH -- Grace. Boyd gave her a virus that attacked her tumor. Apparently, some viruses have been known to attack cancerous tumors before they attack the rest of the body, which means that everyone with terminal cancer watching this show just left to get their hands on any and all viruses around. One thing that is known to go after the exact kind of cancer cells that Grace has is herpes. Herpes encephalitis explains all of Boyd's recent symptoms.
Boyd may have a fever, but he's still got enough fight left in him to fend off House, when House tries to remove Boyd's shirt to find the herpes encephalitis sore that he must have scratched before putting his hand on Grace's face, thereby transmitting the virus to her. Boyd's dad wakes up, and asks how Boyd could have gotten herpes without having sex. The answer is that he couldn't. Boyd had some sinful, God-hating premarital sex, and now he gets to pay a price for it that's even worse than anything 7th Heaven ever came up with. Boyd starts panicking, and says that he is clean. House appeals to his father, asking him why he thinks Boyd is so desperate to purify himself with all that water consumption if he hasn't done something to make himself feel dirty. Boyd begs his father to have faith in him. "I have faith in the Lord," says Boyd's dad. "You, I trust. As much as you can trust a teenage boy." Uh oh. Boyd's dad orders him to take off his clothes for House. Boyd sinks down on the bed, and pulls up his shirt, revealing telltale sores on his back. House assures him that he'll recover from this, and the doctors leave the room, Boyd curled up in his bed, his face buried in his pillow in shame. Aw, I feel sorry for him. But how did Boyd know that those sores, which were nowhere near where you'd expect to find herpes, were related to his sinful sex and, therefore, something he needed to hide from everyone? I guess he read the script.