Like... If, say, the drugs were placed in the envelope to be sent to, say, Man #3, and not Woman #1 -- the person who died, in this case -- so that they could kill M3 instead of W1, though unintentionally it got to W1 before it got to M3. That might be kind of confusing, sorry. Dragonstar might be able to help explain it, since we have similar thoguht processes.
Someone was trying to send the drug to someone else, but this woman used the letter that had already had the drugs placed in it and she didn't kno. Then she breathed it in and died. That's what he's trying to say....right?