Guthrie's back at the police station, and this time he's in the interrogation room. Gregson would like a blood sample for a better DNA test. Holmes spots some evasions and asks if Guthrie had leukemia. Yes, five years ago. Holmes alleges that the blood at the crime scene came from his body, but it had someone else's DNA because of the bone marrow transfer. Oh, really. To be fair, this is the kind of goofy twist that traditional Holmes stories are sometimes built on. Holmes alleges, "You stole forty million dollars and then you murdered two people." Guthrie would like to leave. But Gregson has a court order for the blood. Gregson says that maybe if he gives up Amelie, that would help.
Holmes is annoyed that Casterly Rock Security gave him four $500 bottles of champagne when he can't even drink. He offers them to Watson, since she spotted the bone marrow. She thinks it would be rude to drink in front of him. It would! What kind of sober companion gets drunk in front of their client? Watson pours out the champagne as she and Holmes banter about whether he's really the smartest man in the world. He's willing to admit that it hasn't been conclusively proven. I was hoping he'd mention his smarter brother.
The doorbell rings. Holmes gets it, and it's Watson's mother. Holmes cheerfully says, "I'll leave you two to chat." Mrs. Watson says the place seems to suit her client. She thinks that Watson just doesn't seem happy sober-companioning. It seems like she picked this job out of a sense of duty because of her job (killed a patient) and love life (ex-boyfriend became an addict). But when the two of them talked about Sherlock's work, there was a sense of excitement. Watson admits that she likes what Sherlock, but she's not a detective. Her mother asks, "Will the next client make you happy? People find their paths in the strangest of ways." Holmes comes in. There's something on the news! The Pieta has been returned by courier. The police think the thief must have been suffering from a guilty conscience. Holmes pauses a little longer than necessary, then leaves.