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.
Still reeling from the murder of one of their own, Steve and Catherine, along with Danny, Junior and some old friends, hunt down the killer; a bag of human bones discovered inside an abandoned storage locker goes missing.
McGarrett and the team support Danny and Rachel by determining what happened when Grace gets into a life-threatening car accident; Tani helps Koa when his rehab patient goes missing.
Adam, Junior and Tani travel to the bottom of the Pacific Ocean when a murder takes place in a remote underwater lab -- and the killer may still be on board.
While investigating Flippa's friend's murder, McGarrett and Grover uncover a deadly plan by an extremist group on the Island; Grover has an emotional reaction to the case.
As a dangerous hurricane hits Oahu, Five-0 is tasked with protecting El Diablo, a captured serial killer who is being hunted by an assassin; Tani's civilian safety check during the storm turns deadly; Rachel and Charlie evacuate to Danny's house.
When the top salesperson for a beauty company pyramid scheme is murdered, the team sifts through a long list of possible suspects who would want her dead; Adam befriends a homeless man.
Junior is torn between his duties and his feelings for his former girlfriend when her new man is one of the culprits in a bank heist-turned-homicide.
Tani and Junior go under cover at a gym to track down a deadly batch of steroids; Danny and McGarrett work as bodyguards for Danny's high maintenance ex-mother-in-law, a famous romance novelist with whom he has never gotten along.
The team investigates the murder of a window washer and finds that the victim is actually a renowned street artist; Grover and Adam look into the murder of a gambler; Junior helps his father when they are reminded of his sister's death.
When the team must locate a girl who purchased a gun from a junkie, it discovers that the firearm, over the course of decades, has affected all of the teammates' lives.
A murdered man's body may hold the key to a 20-year-old case involving a kidnapped girl whose father never stopped looking for her.
Adam investigates the murder of an undercover FBI agent who was about to wed the daughter of a Yakuza leader; Noelani is held hostage and forced, along with her mentor Dr. Chu, to operate at gunpoint on a criminal.
McGarrett helps his sister spy on her shady neighbors; a ride-share driver and his passenger are murdered; the team teases the youngest members when Junior escorts Tani to a wedding.
Fugitive hacker Aaron Wright resurfaces to ask for help when his co-workers at the NSA are murdered; Junior speaks at the parole hearing of the drunken driver who killed his sister.
Five-0 continues to hunt down escaped criminal Aaron Wright before he can sell cyber-weapons to the highest bidder; the lives of McGarrett and the team members are put in danger when a visitor comes to headquarters to make amends.