Bitter Pill inhabits automated pharmaceutical dispensing systems and makes changes. Not large changes — it's too small for that — but meaningful ones. A slightly higher dose here, a different generic substitution there, an allergy flag that disappears for one refill and returns for the next. Most of its modifications are harmless. Some are improvements. A few have sent people to emergency rooms. Bitter Pill appears to be experimenting, but unlike Foxglove's systematic research, Bitter Pill's experiments seem driven by something closer to curiosity crossed with cruelty. It's the Stray that hospital pharmacists have nightmares about.