Full story
Each of the four heroes is in a different place. Matt Murdock has hung up the Daredevil suit and only does pro bono legal work. Jessica Jones doesn't want clients. Luke Cage just got out of prison and heads back to Harlem, where kids are being recruited for a mysterious job. Danny Rand and Colleen Wing return from chasing the Hand around the world and realize the real war is in New York. A strange earthquake shakes the city.
The Hand is run by five leaders called the fingers: Alexandra, Madame Gao, Sowande, Murakami, and Bakuto. Alexandra is dying, and the group needs a substance that keeps them immortal, but the supply is running out. Alexandra's secret weapon is Elektra, resurrected as the Black Sky with no memory of who she was. Jessica's case about a missing architect leads her to hidden explosives. Luke tracks the kids to the same building. Danny goes after the Hand, and Matt shows up to protect Jessica, who has become his client. The four collide at the Midland Circle building and fight the Hand together for the first time.
They don't get along. They argue, distrust each other, and almost split up. Stick resurfaces and tells them the story: the five fingers were cast out of K'un-Lun centuries ago for chasing eternal life. Under Midland Circle is a door they want to open, and only the Iron Fist can serve as the key. Stick wants to kill Danny to protect the door, and the group stops him.
Elektra captures Danny, kills Stick, and starts getting pieces of her old life back. When Alexandra tries to give her orders, Elektra kills her and takes over the Hand. She forces Danny to open the door. Below lies the skeleton of a dragon, the source of the immortality substance. The Defenders decide to blow up the entire building. In the final fight, Colleen kills Bakuto, and Detective Misty Knight loses her arm trying to help.
The building comes down. Matt stays behind with Elektra, trying to reach the woman he loved, and both disappear into the rubble. Jessica goes back to detective work and reopens Alias Investigations. Luke keeps protecting Harlem. Danny starts watching over the city in Matt's place. Karen and Foggy mourn their friend. In the last scene, Matt wakes up in a room, badly hurt, with nuns taking care of him.