Whew, what a season! First we went back in time for an adventure that took place around the middle of Season 2 (shortly after Murphy's daughter Lucy was born). Here we met who would end up being the main antagonist of Season 3: a fella known only as The Man. He works for Zona, collecting scientists and God knows what else for their nefarious schemes … and proved to be quite the formidable foe for Operation Bitemark.
From there, we picked up where we left off at the end of Season 2, with Murphy escaping from the Zona submarine via speedboat. He had the wounded 10K on board with him, along with Dr. Merch, who's now under Murphy's mind control.
Meanwhile, Roberta, Doc, Addy and Hector (the cartel enforcer formerly known as Escorpion) are being held at gunpoint by Pan Asian soldiers. The leader of this squad is Dr. Sun Mei, who's come all the way from Beijing to track down The Murphy and cultivate a cure for the zombie virus. After some initial tension, Sun Mei proves to be quite the formidable ally for Operation Bitemark.
Elsewhere, Citizen Z is rescued from the elements by a spirited Inuit girl named Kaya. The two strike up a super-cute romance, with Kaya's Nana and Uncle Kaskae looking on.
Murphy breaks off from Operation Bitemark and sets up shop at the Museum of Progress in Spokane. There, he starts building his army of Blends, half-human/half-zombies that worship Murphy as the new Messiah. 10K hates being Murphy's personal sniper and cleaning boy, though he doesn't have much choice after receiving a mind-controlling Murphy bite.
Dr. Merch is in charge of cultivating Murphy's Blend vaccine, though she soon becomes disillusioned with being Murphy's slave and commits suicide. Murphy gains all of Dr. Merch's intelligence by eating her brains and is able to create the vaccine on his own.
In hot pursuit of Murphy, Roberta and the gang end up in the small town of McCloud, where they meet its only human resident: Barney Becker. It would appear that Barney went postal on the citizens of McCloud and they all turned Z … and now follow the man who murdered them around everywhere. Barney's attempt to add Roberta and the gang to the horde backfires horribly and he becomes a Z himself.
Next, the gang runs afoul of the Red Hand, a group of extremist vigilantes lead by someone who calls himself Escorpion. Who's stolen Hector's old handle …?
Back in Spokane, 10K manages to escape from Murphy's stronghold and has quite the adventure in the surrounding wilderness. He is guided by visions of two characters we met (and who supposedly died) in the season's first episode: Red, 10K's would-be love interest, and 5K, a young boy raised by crows (seriously).
Doc is separated from the group and ends up at the Serenity Falls Institution for the Criminally Insane, a mental asylum filled with a ragtag group of patients lorded over by the megalomaniacal Nurse Ratched.
There, Doc is reunited with 10K, who's all messed up due to his lack of the original vaccine that keeps him from falling under Murphy's control. Doc and 10K manage to escape after zombies invade the loony bin and are reunited with Roberta, Sun Mei, Addy and Hector.
Meanwhile, The Man has infiltrated the Museum of Progress, assigned to take Murphy back to Zona. After being outsmarted and captured by Murphy, The Man escapes with a new mission: find Murphy's daughter, Lucy, who perhaps inherited her father's immunity and therefore might be instrumental in developing a cure for the zombie virus.
As Roberta, Sun Mei, Hector and 10K head to Spokane to confront Murphy, Doc and Addy head to Springfield, IL to hopefully find Lucy before The Man does.
En route to Lucy, Doc and Addy run into some old friends: Sketchy and Skeezy, whose latest con involves posing as the President of the United States and his 'spiritual advisor.' It all ends in a small town shoot-out, of course.
After 10K makes a run for it upon being discovered as one of Murphy's Blends, Roberta, Sun Mei and Hector look to recruit the Red Hand to invade what's now being referred to as Murphytown. They meet their leader, the man who calls himself Escorpion … and it's Vasquez, the long-lost member of Operation Bitemark! Roberta releases Vasquez from his madness, though not before he kills Hector in retribution for the murders of his wife and daughter …
… well, maybe 'kill' is too strong a word. Either way, Roberta's now in charge of the Red Hand, and off they go to Spokane to take on Murphy and his army of Blends.
Doc and Addy finally make it to Lucy, who's aging at a rapid rate (and is just cute as all get-out). She spends her time with her adoptive parents, playing with the various zombies that wander around outside the house. Doc and Addy almost succeed in getting Lucy to join them on a road trip to see her daddy, Murphy …
… until The Man shows up and kidnaps her. Doc and Addy split up, with Doc assigned to update Roberta via a nearby radio tower and Addy in hot pursuit of The Man.
Meanwhile, Roberta, Sun Mei and the Red Hand descend upon Murphytown. 10K, who has since been recaptured and re-Blended, finally seems to snap out of it after getting a focus assist from an unlikely source: Red and 5K! It looks like they're not just hallucinations after all.
After briefly engaging in fisticuffs, Roberta and Murphy call a truce upon the unexpected arrival of Citizen Z via biplane. He gives them Doc's message about Lucy being kidnapped by The Man, which prompts Roberta and Murphy to join forces and plan a rescue mission.
Addy has since managed to catch up to the kidnapped Lucy (who has since experienced yet another sudden growth spurt), which sets off a series of increasingly brutal mini-battles between her and The Man. The Man emerges the victor and takes off with Lucy (who experiences yet another sudden growth spurt and is now a sullen teenager), leaving Addy battered and bruised but bound and determined to not give up. Go Aunt Addy!
The Man and Lucy arrive at Mount Casey, where an aircraft will take them to Zona. Roberta, Murphy, Doc, Addy, 10K, Sun Mei, Red and 5K arrive and there's a tense face off at the top of the mountain.
The season ends with Addy, The Man, Lucy and 5K falling off the edge of the mountain, seemingly plummeting to their doom …
… Murphy and Roberta both shot through the stomach by The Man …
… and the Zona aircraft opening fire on everyone still at the top of the mountain.