Da Vinci reopens several cases, causing a further rift with his ex-wife.

Da Vinci is convinced a serial murderer has been on the loose for years.

When television news reporter Hope Martin (Lynda Boyd) breaks a story about mercy killing, Detectives Leary and Shannon start digging around for more details, and Da Vinci calls a Coroner's Inquest to force Martin to reveal her source. The issue of euthanasia is divisive and as the investigation proceeds Da Vinci finds himself at odds with the police and his superiors about the reality and the ethics of what happened. His elderly father's recent debilitating stroke further complicates his response. Danny Leary is back in town, but the reunion with his older brother Mick is far from idyllic. It looks like he is hooked on drugs and, unbeknownst to Mick, hanging around with two hoods that turn up dead.

Following a rash of fatal drug overdoses, Da Vinci learns that one of the dead addicts had an infant, who is missing. Manny, a police informer leads Leary, with new partner Angela Kosmo, to the woman's drug dealers. They arrest Todd and Sioux, and through them Larry discovers that the killer heroin came from a French-Canadian supplier who, along with his partner, was murdered, gang-execution style, just days previously.

The Coroner's office investigates the cause of a devastating fire at a seniors' care facility that left most of the residents dead and an elderly man missing. Arson or accident may have caused the fire but while he investigates with Chief Fire Investigator Henry Whiteside, Da Vinci uncovers evidence of abuse at the home. The harsh realities of caring for the elderly are brought into sharp focus by his own mother's increasing inability to care for his father alone. Mick's partner Kosmo and his brother Danny have struck up a friendship that has the potential for a romance. Danny's club looks like it might get off the ground, although his business partners appear to be mob-connected.

When a young woman's dead body is dumped in an underground parking lot with no apparent signs of injury, Da Vinci and the police are intrigued. Patricia's autopsy turns up surprising answers and Da Vinci's investigation draws him into the world of S&M. Someone with a lot of power is trying to manipulate Chief Coroner James Flynn and Da Vinci into keeping the facts and the faces of those involved with Mistress Harriet hidden.

When a street kid turns up dead on the dockside Leary is convinced that the young runaway was tortured to death by other kids and Sunny backs up his theory. The killing reminds Da Vinci of a tragedy in his past in which a police investigation proved fruitless. Determined not to let that happen in this case, Da Vinci pursues a suspect who may help him resolve whether police negligence was involved in the boy's death.

Da Vinci has fallen off the wagon in a big way with a drunken evening at the police bar, which he can't remember. A homeless man is critically injured in a hit-and-run accident in the alley behind the bar on the same night, and Da Vinci comes under suspicion. All the enemies he's made over his career come out of the woodwork, anxious to see him implicated in the crime. Da Vinci's current investigation involves the discovery of a buried skeleton found beneath the Burrard Street Bridge. As Da Vinci struggles to piece together what happened to the homeless man, he stumbles on surprising insights into the Burrard Bridge death.

Patricia Da Vinci's career is on a high when she is asked to be a guest speaker at the prestigious Seattle Homicide Conference. Her presentation involves the recent case of the prostitute serial killer Charlie Josephs, who himself was found murdered. Her re-examination of the case leads to the discovery of several discrepancies and uncovers some new clues in Joseph's death, clues that seem to implicate the police. Sioux, who is now a police informant for Kosmo, implicates Danny in the drug trade and Kosmo is forced to examine her feelings for him.

Da Vinci, Leary, and Sunny are in Seattle attending an international Homicide Conference. A presentation by San Francisco-based FBI Special Agent Charlotte Turner turns up similar cases across the Pacific Northwest, and appears to include the death Da Vinci is currently working to solve. Turner comes to Vancouver and Da Vinci finds himself coordinating an investigation that has international implications. As more abductions/murders fit the pattern it seems that a couple, Dean and his wife Mona, are responsible. Joanna, a young woman who was abducted but managed to escape, leads Shannon and Leary back to the farmhouse where she was held and they arrest Dean. Mona, however, has managed to sneak across the border into the States and Da Vinci offers Danny a deal if he can find out where she is. Meanwhile Da Vinci finds himself struggling with the ethics of paying Dean for information about other victims.

Da Vinci, Leary and Sunny are in Seattle at a conference, and are shocked to discover similar cases across the Pacific Northwest, that appears to include the death Da Vinci is currently working to solve.