Maillol files a request for someone at eighth circle and higher who can cast Detect Thoughts, and/or somebody with very high Splendour who can talk to Keltham about where he's getting his deductions and also talk with him about Carissa Sevar's sexuality, and about her need to be in somebody else's power, and possibly (he's not sure how the details of this could look but he's not the one with the Splendour) manage to introduce the topic of wanting to rent Sevar from Keltham in a way that won't set him off or look wildly implausible.
Maillol isn't going to realize for a while the incredible depth and thoroughness of the blunder he's just committed, and by the time he does, it will be far too late.