The Five-0 Team and SWAT, led by Grover, are entering the location of an exchange of untraceable weapons. They find nothing and assume their tip is bad. McGarrett thanks Grover for the backup, and everyone disperses. As Danny and McGarrett leave, McGarrett hears a ringing. The two open a door off the parking garage and find a man tied up and gagged. Removing the cell phone from the man’s pocket and taking his gag off, McGarrett asks who did that to him. The man replies, “Bomb,” and seconds later, the building explodes, trapping Danny and McGarrett.
Revert back 14 hours. Danny’s new love interest, Amber, meets Grace unexpectedly when she goes into the kitchen wearing Danny’s shirt. Grace is behind the refrigerator door when Amber closes it.
Upset that this is the way Amber and Grace meet, Danny goes to see McGarrett to talk about it. McGarrett’s cell rings, and he and Danny go to Halawa Prison, where Jason Decker has asked to see them. Five-0 is the reason Decker is in prison.
Decker tells Danny and McGarrett he wants a deal – to be put in a minimum security facility and his sentence cut in half. He has information for them. A supplier out of the Philippines is bringing in a big gun shipment with no serials in an hour.
Back to exploded building. McGarrett regains consciousness. He checks his cell but there’s no service. He then looks for Danny. He finds him underneath some rubble and large rocks and must free him. Danny is also injured. On top side, HPD is on scene trying to find Danny and McGarrett.
Meanwhile, Chin and Kono go to Decker and get nowhere. They decide to pull his visitor log and phone records.
McGarrett decides he and Danny should make some noise. Maybe someone will hear them. They find pieces of pipe and begin to beat against anything that will make a noise. Catherine hears the banging, and they try to triangulate the noise. Catherine gets an idea to get McGarrett’s cell to ring, and it works. McGarrett tells them he and Danny are in the maintenance room on the south side of the garage. Grover tells them everything is unsteady, and another cave-in is possible. Catherine arranges a video call and manages to capture a photo of the man who was tied up and is now dead.
Danny has found some pills in the man’s pocket, and Max says they are anticoagulants. Since the man is so healthy looking, Max doubts the pills are for a heart condition and asks McGarrett to check for scarring from a surgery, perhaps gall bladder or kidney surgery. McGarrett does find a scar, and Max believes it is indicative of a surgery within the last three months.
When area hospitals are checked, Kono brings the results in a file to Chin. Catherine says they can run the names through DMV to see if anything comes back. Chin stops her and says there’s probably no need. The first name in the folder is Marcus Decker, Jason Decker’s younger brother. Decker has been working with the ATF for months, and they believe someone decided to kill his younger brother for revenge. When Kono and Chin show the photo of his brother to Decker, he tells them a guy on his cell block named Spider gave him the intel. Spider is a lifer and probably not interested in anything they have to say. Kono thinks otherwise. When Decker and Spider are alone in a cell, Decker makes Spider talk.
Back at the building site, HPD needs to get Danny and McGarrett to move 30 yards. Perhaps they can get them out through the ventilator shaft.
Decker tells Chin and Kono that Spider has paid him $5,000 and promised him 20 more if he will get Five-0 to the garage. He has used a contraband phone to communicate with someone on the outside. He also convinces Decker that the ATF is not being straight with him.
While Danny and McGarrett try to maneuver 30 yards, there is another cave-in. All cell contact is lost. McGarrett looks for a way out and gets an idea. He uses a grenade on his belt and some pipe to blow a way out, and the pair are lifted to safety.
Once outside and safe, Chin tells McGarrett that the burner phone traces back to an Edward Cobb, ex-CIA in Chinatown. He used to run Black Ops in Southeast Asia in the seventies.
McGarrett surmises this explosion is not about Five-0 at all. It’s about his mother.
McGarrett calls Cobb on the phone, then shows up at his office while still on the line. He forces Cobb to tell him who is in the grave in Cambodia. It’s Wo Fat’s mother, who was mistakenly killed when Wo Fat’s father was the target. Wo Fat’s father is still alive. McGarrett surmises that Cobb ordered an unsanctioned hit. When Cobb goes for a hidden gun under his desk, McGarrett shoots and kills him. He is left to wonder what’s next.