Yeah, totally. All we have seen so far lead's us to think that he is responsible ofAnna's father dead. The idea of Anna falling into Grant claws by the action of one magic pill isn't my favorite from all the ideas I think that path can go. It's true that Mr. Palmer said something about the drugs tag, so maybe this is the situation he will introduce them.
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For the audience having Grant drug Anna would be pretty weak as far as plots go. Considering the following factors; first, it flies in the face of Anna's bio about already having a high sex drive and a wild side to her libido-- a knocked out Anna getting railed by Grant wouldn't be as satisfying because it's not her fault (it's fair to say folks want to see Anna struggle with her moral conscience and the desires of her body). Second, using drugs to date-rape Anna is illegal and Grant is an attorney--though it's not a bullet proof argument that would prevent Grant using drugs on Anna, it's still a thing to consider.
Plus, it might not be that easy to slip Anna a drug--if offered a drink she just might not want to drink it. Grant wants to have a real shot at Anna and too many things can go wrong leaving him blue balled. And I suspect Grant doesn't want an unconscienced fish to play with.
First, Grant has to win back Anna's trust. Getting a "one time" roll with Anna would be rather disappointing from Grant's point of view. He has had years of wanting Anna and I doubt one evening with her would scratch that itch. So... Grant has to get back into Anna's good graces (I've already written a plausible reconciliation encounter), but more so he has to have a powerfully emotional reunion with Anna to put her off her guard and make Anna see herself as the bad guy to herself so her and Grant can go back to the way things used to be before the funeral.
From the context of the story, the main factor is Anna getting her freak on with Grant, but more so when it is Anna who goes to seek Grant out for a "special service." Then perhaps somehow for some reason they have a relationship. But with all the male love interests it's all of them going to make a move on Anna. But for the main plot of the story is how Anna reacts to those moves, responds to those moves, and eventually its Anna making moves herself.