In Serving Life, a mysterious doctor is wandering the halls of the Emergency Department of the Gursky Memorial Hospital, providing medication to patients suffering from dementia. Annie is suspicious of his motives and is determined to identify the man. Her search kicks into high gear when some of the dementia patients die unexpectedly. Gilles is assigned to investigate the murder of a doctor who is in charge of a research lab at the Gursky.
At the same time, a serial killer is stalking the streets of Montreal, killing people apparently at random. Gilles and Annie team up to uncover the clues that link all the crimes and ultimately to solve them.