My entire training is a war against jumping to conclusions; you do not diagnose a murder because a finding is strange, you rule out the innocent explanations first, methodically, one by one.

So I tried.

I tried to build an accident.

A mix-up at a pharmacy — but this compound is not dispensed at pharmacies.

A patch meant for someone else, applied in error — but it had been placed with care, beneath the collarbone, where the skin is thin and the absorption is fast, on the one woman in the state for whom its contents were lethal.

A tragic coincidence of the universe — but the universe does not know which specific molecule will kill which specific woman, and does not go to the trouble of obtaining a restricted compound to deliver it.