Having assembled something brilliant out of bikes and refuse, the Doctor -- with Amy standing by on the bluetooth -- scans the upstairs. But there's nothing really going on up there. "Only for you could too normal be a problem," Amy scoffs. "You said I could be lost forever? Just go upstairs!" The Doctor's feeling cautious, for once, and then realizes Amy can get him the plans, which will reveal that -- much like the house in Ledworth -- there are floors and doors that shouldn't be. Little does the Doctor know that right outside, Craig has decided to touch the rot on the ceiling, muttering "Rotmeister" darkly under his breath.
Next morning, the Doctor -- knowing how rough last night was on him -- brings Craig breakfast. Craig is not doing so well, having touched the rot, and is near comatose. The Doctor gets incredibly frightened for him, desperate and wild-eyed, and starts yelling: "What's that? An unfamiliar and obviously poisonous substance? Oh, I know what would be really clever, I'll stick my hand in it!"
Home. A little bit of home, dying in front of him. Amy in danger so terrible he can barely admit it. All alone in the world at the bedside of a dying man.
The Doctor works and works, like a doctor, until he can get Craig to breathe; runs out in the kitchen to find stuff to "reverse the enzyme decay" and "excite the tannin molecules," and after a bit longer he's got Craig living again. Of course Craig immediately is off to work, but the Doctor makes him stay down. "It's the planning meeting!" The one that will save him, and the company, and make him something special. His orangutan habitat: "It's important!" he tries to shout, falling back against the bedclothes. "You're important," the Doctor hums, more lovingly than almost anything I can think of him saying this year. "You're going to be fine, Craig."
Hours later, Craig wakes up refreshed... And having missed the meeting by a mile. He goes running into work, screaming at himself and apologizing profusely to his boss, until he notices the Doctor at his desk, on his phones, talking shit to his ruder clients. "Craig, how are you feeling? Had some time to kill, I was curious, never worked in an office. Never worked in anywhere." Craig tries to throttle him, but bossman tells him to be nice. "Leave off the Doctor, I love the Doctor! He was brilliant in the planning meeting."