So, right from the start, there’s just nothing beyond Bruce’s insistence to suggest that Claire didn’t kill herself. The retired investigator never found anything unusual; Claire’s mom had been expecting the call for years. The detectives interview Adam, and he’s genuinely regretful that he might have contributed to Claire’s death–the drugs were his. But he’s such an open book, so much the opposite of the opportunistic douche Bruce portrays him as–and, more importantly, that he portrays his past self as–that there’s just nothing to go on.
But among the drugs in Claire’s system is an anti-emetic (ie, keeps you from vomiting), a common practice in suicide by pills, except that the detectives back in 1998 collected all the medication in the house and no anti-emetic was found. And the pills that killed her were opiates, unlike the diazopenes that the bottle says they are. They track down Adam’s old dealer, and convince him that they’re not interested in busting him, and he tells them that he never sold Adam the opiates, because they were too hard of drugs for him to risk.
So, did Claire find street drugs to kill herself, and just used all the anti-emetic or put the bottle someplace where the detectives in 1998, who were totally going through the motions, didn’t find it? Or is there something more sinister afoot? The plot thickens when Claire’s mom is tracked down: the handwriting on the suicide note is only a sort-of match for Claire’s old journals. And there’s the matter of the fingerprint on the bottle with the opiates in it, which doesn’t match Adam, Bruce, Claire or the dealer.
If you’ve read a lot of these, you might have already figured out what really happened…