Based on the "girl in the box" sex-slave case, in which Cameron Hooker and his wife, Janice Hooker, abducted Colleen Stan (a.k.a. Carol Smith), then kept her captive and tortured her for seven years.
This is the last episode in which Robert Palm serves as executive producer/showrunner. Palm, who was showrunner for only the first season, left the series as he felt too disturbed by the show's dark subject matter. He was replaced by Neal Baer starting in the following season.
The veterinary medication described as "Beuthanasia" is actually phenobarbital. In reality, it truly is neon pink and used to put down animals as described, but human use is common. The drug, in pill form, was a commonly prescribed sleeping pill abused recreationally in the 1960s and 70s. It was sold under the trade name Luminal and was better known by its street name "reds".