After McGarrett's CIA agent friend is killed, he lets himself be captured by the group he thinks is responsible to find the killer; Tani questions whether she should tell McGarrett about the murder weapon she found at Adam's house.

When a vacationing father on a flight to Honolulu is kidnapped and forced to parachute midflight, Danny, Tani and Junior track him through the jungle to discover that he may not be who he seems; McGarrett is threatened with a secret from his past.

A heat wave hits Oahu, contributing to a spike in crime; McGarrett and Danny hunt down a bank thief; Tani and Junior's car is stolen while they're on duty; Kamekona incites a riot by price-gouging his ice.

Jerry accompanies Junior as he escorts a fallen soldier home to Oahu; McGarrett and Danny discover a body when they delve into the highly profitable black market for sand.

On Halloween, Jerry and his friends search his childhood camp for evidence to a murder he witnessed as a boy; McGarrett investigates a little girl who drew pictures depicting the scene of a recent murder before it was discovered.

McGarrett crosses the line and is arrested while investigating the death of his former SEAL buddy who died while making an emergency landing on an aircraft carrier; Adam returns to Oahu with devastating news about his marriage.

McGarrett investigates a cold case that his grandfather and the famous Honolulu detective Chang Apana worked on in the 1940s; McGarrett and Danny get ready for the opening of their restaurant.

Grover's parents and brother arrive in Oahu for Thanksgiving; a thief is crushed to death by an empty safe.

When a renowned urban vigilante is killed after making a citizen's arrest, the team delves into the world of super heroes and comic books to find the killer; Adam gets closer to finding out who killed his sister.

After fighting off an assassin in his own home, McGarrett and Joe White flee to Montana to prepare for a battle against those exacting revenge for a past SEAL mission.