Ah. Lancelot doesn't know a huge amount about vampires, as a rule. He hasn't interacted with them too much, doesn't know a lot about how they behave. However, he imagines that like any people they don't take kindly to unannounced visitors. And he can infer that, perhaps, Kenzi wasn't making a polite house-call to chat.

"They weren't happy about it, I assume?"