The day after celebrating his son Jason's tenth birthday, Ethan Mars (Pascal Langdale) and his family go shopping. Jason and Ethan are hit by a car; Jason dies, and Ethan falls into a six-month coma. After he wakes from the coma, Ethan, blaming himself for Jason's death, separates from his wife Grace and moves into a small suburban duplex while experiencing mental trauma and blackouts. Two years later, Ethan blacks out at the park with his other son Shaun.

When he wakes up, he discovers that Shaun has been kidnapped by the "Origami Killer", a serial killer whose modus operandi consists of abducting young boys during the fall season, drowning them in rainwater, and leaving an orchid on their chests and an origami figure nearby. Norman Jayden (Leon Ockenden), an FBI profiler struggling with addiction to a drug called Triptocaine, investigates the death of another Origami Killer victim and concludes that he died the same day as a violent rainstorm, which flooded the cell where he was kept. He estimates that Shaun has only three days to live based on weather patterns.

Besieged by reporters, Ethan checks into a motel. He receives a letter from the killer, which leads to a shoebox containing a mobile phone, a handgun, and five origami figures. The killer calls him and explains that each figure contains instructions on completing tests that will determine how much Ethan loves his son. Every time he completes one, he will receive a piece of the address where Shaun is held.

The tests include driving against traffic at speed on the highway, crawling through broken glass and active electrical pylons, cutting off one of his fingers, murdering drug dealer Brad Silver, and drinking poison on camera. Ethan meets Madison Paige (Jacqui Ainsley/Judi Beecher), a journalist who sometimes uses the motel to deal with her insomnia. She decides to conduct her own investigation into the Origami Killer.

Jayden and his partner Lieutenant Carter Blake investigate suspects, but nothing pans out until Grace arrives at the station, fearing that her estranged husband is involved in Shaun's disappearance. After Ethan's psychiatrist, Clarence Dupré, reveals that his patient has a history of blackouts, Blake and his superiors put out a warrant for his arrest. Unconvinced, Jayden continues to investigate other leads.

Meanwhile, private investigator Scott Shelby (Sam Douglas) meets the families of the Origami Killer's victims, collecting the letters and other items they received when their loved ones were abducted. Prostitute Lauren Winter, a victim's mother, persuades Scott to let her accompany him. Their investigation leads them to Gordi Kramer, who claims to be the killer, but when they attempt to question him, they are knocked out and wake up in a car sinking to the bottom of a lake.

After either saving or failing to rescue Lauren, Scott tracks down Gordi's father, Charles, and forces him to confess that his son was responsible for an earlier incident in which a boy was killed.