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After The Defenders, Danny Rand promised Matt Murdock he'd look after New York. He lives with Colleen Wing at her dojo in Chinatown, works for a moving company and patrols the streets at night. The local gangs, the Golden Tigers and the Hatchets, are on the edge of war, and Danny tries to keep the peace with his fists.
The trouble comes from close to home. Davos, who grew up with Danny in K'un-Lun, believes the Iron Fist should always have been his. He teams up with Joy Meachum, who wants revenge on Danny and her brother Ward for everything she lost. They hire Mary Walker, an ex-soldier with split personalities, to spy on the couple. Joy finds an ancient bowl, and Davos performs a ritual using the tattooed skin of a past Iron Fist and Danny's blood. The power passes to him, and Danny is left nearly dead.
With his fist glowing, Davos becomes a brutal vigilante. He kills the gang leaders, recruits street kids and starts his own war on crime. Danny, powerless, has to learn to fight all over again. Ward tries to quit drinking and finds out he's going to be a father. Joy realizes too late that Davos is not the ally she thought. Misty Knight joins the hunt with the police, and Mary, or rather her other half, decides to act on her own.
In the final showdown, a new ritual gets interrupted halfway and the power splits between Davos and Colleen. Colleen pulls the rest of the energy out of him and becomes the new Iron Fist. Davos loses the power and is arrested. Danny realizes he needs to understand his own history better and leaves the city in Colleen's hands.
The season closes with Danny and Ward traveling through Asia in search of the Iron Fist's past. In the last scene, in Japan, Danny fires two pistols charged with his chi. Colleen stays in New York with her sword glowing. It was the end of the series.