Watson's step is so happy, Holmes can nearly take that as confirmation of what has gone on over at Miss Morstan's home; what Watson says nearly confirms it. If it hasn't taken place tonight, then it will happen soon enough. Holmes isn't sure if he ought to make moves to stop it. Is it fair to keep Watson to himself? To stop him having a normal life, not that that's always a good thing? Certainly stopping him from having children is enough to feel guilty about.

"I'm sure you're quite entangled," he says venomously, glaring into the distance. "You ought to have stayed later. You're clearly welcome there."