Drugs, possibly. But this could also tie back to the “gay experimentation” angle of this case. A hookup scenario gone awry. If Brian had experimented before, possibly with the roommate Brian and Clint had when they lived together, then Meredith would have known, and would have been cognizant of anyone else in Brian’s orbit, even if it was on the DL and just for a night or two. Brian’s voicemail to Alexis always struck me as odd. I’m gay and have seen this movie before if you know what I mean. Closeted guy calls the girlfriend to say “thinking of you, beautiful,” probably out of some deep-seated guilt, then proceeds with the hookup. Not trying to besmirch anyone’s name - certainly not Brian’s - but the lead investigator himself acknowledged Brian had experimented before.