When the bodies of two serial killers are found on Five-0 property with chess pieces in their mouths, McGarrett and the team hunt for a vigilante as fear grows that tourists aren't safe in Hawaii.

Five-0 must work with rogue MI-6 agent Harry Langford to find a terrorist planning to cause nuclear reactors across Europe to meltdown. Also, McGarrett and Danny ask retired FBI profiler Alicia Brown to help them find their serial killer vigilante. Written by CBS

Alicia Brown finds a dead body in her bed, which was placed by the serial killer 5-0 is looking for. A girl whom Kono knew when she was surfing calls her because she was arrested on a drunk and disorderly. Kono discovers she's an amputee and homeless. The team gets an unusual case, wherein a homeowner was shot and a man literally fell out of the sky. They learn the man might be connected to a DEA case. Written by rcs0411@yahoo.com

Five-0 must find McGarrett and Alicia when they are kidnapped by the serial killer they've been hunting.

When an armored vehicle crashes into a gun club, the team is called in. They arrive and the vehicle just stays there, it suddenly moves and stops. Steve goes to apprehend the one inside but he parked on top of a manhole and made his escape. Steve wonders what he was doing, Steve learns the owner keeps some exotic guns and they were all taken. Steve thinks he's going to sell them and there's a man who's a collector of guns whom Steve thinks is the buyer. So they go to the man's house and find him dead. The perp then posts something online that's anti-gun. So they think the perp is an anti-gun guy. They think he's going after all gun advocates but there are so many of them. Adam after getting released, asks Kono to help him find the daughter of an inmate he befriended, who hasn't seen his daughter since he was locked up. Written by rcs0411@yahoo.com

On Halloween, Five-0 investigates the murder of a medium with a checkered past who was apparently scared to death by a poltergeist. Also, Kono and Adam are kidnapped by what appears to be a death cult.

Five-0 must free McGarrett's mother, Doris (Christine Lahti), when Catherine (Michelle Borth) informs them that she was captured and is about to be executed after attempting to free Wo Fat's imprisoned father. Also, Chin loses his appeal to have Sara's adoption delayed, and she must move to Mexico.

When Grace goes to her Winter Formal, Danny offers to chaperon because he wants to know who her date is. When he discovers who it is, he takes him to the bathroom to talk. It's while they're in there that some men with guns come in and take everyone hostage. Danny stays hidden. He can't call anyone because they jammed the cellphones. Eventually Danny confronts one of them and the one he's with thinks he knows why they are here. Grover goes to check on his son who is also there but the guy on the outside won't let him in. But Grover insists on going in that's when he pulls a gun. Grover then calls Steve to come. They eventually find out what's going on and realize they have to go in but they need to know who they are and where they are. The people inside learn about Danny and threaten Grace unless he surrenders which he does. Written by rcs0411@yahoo.com

When Jerry's conspiracy theory friend investigating a possible clue that could solve the mystery behind John F. Kennedy's assassination is killed by a sniper, Jerry finishes the investigation while McGarrett and Danny search for her killer. Written by jgp3553@yahoo.com

Five-0 investigates the 10-year-old cold case of a missing teen when a boy suffering from PTSD undergoes hypnosis and realizes he may have witnessed her murder. Also, Danny's sister, Bridget (guest star Missy Peregrym), visits Oahu for a business conference, and he suspects that she may be getting too close to a co-worker. Written by CBS

Five-0 heads to Mexico where Chin risks his life to rescue his kidnapped niece.

Chin is kidnapped by a cartel in Mexico and Five-0 races to rescue him before he is executed by his vengeful abductors. Meanwhile, Grover goes undercover as a car salesman to investigate a murder that turns out to be far more complex and dangerous than expected.

As Max prepares to say goodbye to his Five-0 ohana, they must investigate a murder during a police convention on the Island.

Five-0 must go up against an aggressive U.S. marshall, Lincoln, when a man wanted for murder escapes capture and seeks asylum in the sovereign land belonging to the Nation of Hawaii.

Five-0 uncovers the possibility that a Nazi war criminal may be hiding in an old leprosy colony.

McGarrett and Danny spend Valentine's Day with their girlfriends, while the rest of Five-0 investigates the murder of a man who had been taking classes on picking up women.

McGarrett and Five-0 once again become entangled in the twisted mind games of serial killer Dr. Madison Gray when she stumbles into HPD covered in blood that matches Alicia Brown's, and claims amnesia.

MacGarrett and Danny finally track down the missing uranium, which has been used to build a bomb located in the middle of the jungle. Now, they must carefully extract the unstable explosive through treacherous terrain before it detonates.

McGarrett and Kono suspect that an abused young girl may be the victim of a sex trafficking ring on the Island. Also, Chin and Grover investigate a murder at a sober living facility.

Five-0 helps PI Harry Brown work the case of a kidnapped wealthy woman whose husband may have something to hide. Also, Rachel tells Danny that she is getting a divorce from Stan.

Steve, Danny, Chin and Kono track nemesis Michelle Shioma to the island of Lanai. However, fearing that she might have allies on the inside of HPD, the team decide to go it alone and when they get there they find out that it's a set up and they are soon captured by Michelle and her yakuza soldiers. Jerry is the only one who knows about the mission and is ordered not to tell anyone on the force including Duke and now must face the dilemma of telling Duke at the risk of the mole finding out or keeping quiet. In the meantime, Lou goes to Chicago to testify against his former friend in his corruption trial. However, he is given a frosty reception by his former buddies on the Chicago PD who view him as a traitor. Written by Brian Washington Sargebri@att.net

While working the murder case of one of the last survivors of the USS Arizona, McGarrett learns about his grandfather's important role at Pearl Harbor. Also, Adam uncovers bone fragments at his new construction job and asks Jerry to help him discreetly investigate.

Danny protects a coma patient showing signs of waking who was the key witness from his last HPD case before he met Steve and joined Five-0. Lori Petty guest stars as Nurse Jenny Kitson, and Michael Paul Chan guest stars as Danny's former HPD Captain, Tanaka.

When McGarrett gets a tip that someone is plotting a terrorirst attack on Oahu, Five-O searches for those behind it before it's too late. Also, Chin and Abby have a very difficult decision to make.

McGarrett puts his life in lethal danger when Five-O puts a risky plan to rescue a group of young girls from a sex trafficking ring in motion, Kono decides to make a life- altering choice beucase of the unique strain caused by the case.