Whether he deduces it or not, given the protection I swore for your service, Mr. Holmes is as much a concern of mine as you are. If there is anything I feel I must know about him to ensure that protection remains whole, I will look into it.

[Of course it isn't all about protecting Sherlock, not entirely. Astaroth is beginning to feel that he may well pose a threat to him, or at least to his mortal cover.]