ION Mystery

A boy from Ralph's class goes missing after having a run-in with a deadly criminal; Toby comes closer to discovering the identity of Happy's husband.

A simple job at the Los Angeles Natural History Museum turns deadly when thieves steal things from a rare gem exhibit to get the materials they need to make a nuclear bomb.

Team Scorpion explores a deep cave system in an effort to prevent a bat population from harming the North American ecosystem; the team dons Halloween costumes for Walter's impending immigration inspection.

After a woman barely escapes death at the hands of a serial killer, Horatio intends to catch the criminal.

The team discovers a club where hunters pursue human prey deep in the Everglades.

The team tries to find a connection between the murders of a truck driver and a woman on his delivery route.

An escaped prisoner takes Natalia hostage and reveals shocking secrets about his crimes.

Horatio must protect a mixed-martial-arts fighter from the guy's brother, a prison escapee.

Catherine and McGarrett go to Afghanistan to help a young boy, whose family saved Catherine years earlier.

Grover is forced to steal $100 million when a nemesis kidnaps his daughter; Wo Fat goes back to Oahu after escaping from prison.

O'ahu goes on lockdown as the team looks for a terrorist who is using weaponized drones on civilians; McGarrett and Danno attend a review with a psychologist.

While a Navy Seal is on a secret mission, his young daughter is kidnapped; Danny must find $18.5 million in order to save his brother.

Three female thieves unwittingly make themselves serious targets when they take something during a tour bus robbery; Danny searches for his brother's money.

When a man from Detroit is killed on the streets of Oahu, the team is shocked to discover the killer's motives; Chin risks everything to help Danny.

McGarrett meets a woman who helps him reopen the last cold case his father investigated before dying.

On Halloween, the team hunts a serial killer who mimics murders from a cult slasher film; Jerry is abducted by counterfeiters.