Helen Dean, an elderly patient at a hospital in New Jersey, suddenly dies. Her son vividly recalls his mother's concern that a stranger unexpectedly injected her hours before her death. The hospital launches an investigation, no answers are found. In the following months, several other mysterious deaths plague local hospitals. The cause remains unknown until a local expert uncovers a series of poisonings. He alerts authorities, and soon investigators hone in on their suspect, a local nurse who's been practicing for 20 years, with a history of mysterious and sudden deaths on his watch.
—Discovery ID website