When a large supply of hair tonic is stolen, Ness and the Untouchables are concerned that it may be used as a base for illegal - and deadly - liquor. Soon after, the stuff starts to appear flavored with ginger jake, a popular patent medicine. The result is a permanent neurological disorder that was first seen in a major outbreak in Kansas City. The first victim in Chicago is Mary Kay Spencer, a 17 year old who drank the stuff while out on a date with her boyfriend. Working with public health officials, Ness tries to track down the source of the deadly hooch.