The episode starts with Sam and Max in Sam's grandma's house, the duo decked out in pajamas and enjoying the quietness of the holidays. However, Sam tells Max that this year would be different as his grandma, Ruth, has big plans this year. They're cut off as mysterious lights shine out from the nearby window - Max thinks it's "the mothership" coming to take them away; Sam thinks its trouble, grabs Max and races for his grandma. They're both wrong as Ruth's at the other side of the front door and she's come to pick them up. In a helicopter.
During the ride, a lot more of Sam's grandma is told: she was the prison warden of Blood Island Penitentiary for 40 years, known there as "the Iron Maiden". And as it turns out, she's taking the two there to help her spread some holiday cheer, something that Max is not fond of at all.
Landing at the Penitentiary, the various inmates quickly surround the helicopter, happy to see her as the new warden tells a nearby guard to hold his fire. However, not everything is so jolly: a group of inmates seek to use her arrival as a means to escape. During a "Visit Ms. Claus" session, the group confront the trio with Sam betting Max that the ringleader, Hurtzog, was "glaringly absent from Santa's 'Nice' list." Ruth proves them right - the man attempted 43 escape attempts. He proclaims he's changed and Sam is willing to give him the benefit of the doubt. Despite her own misgivings, she does so, leading to Max giving him a very hard fruitcake. This proves to be a mistake, as Hurtzog and his cohorts use the fruitcake (and Max as a baseball bat) to kill the power, making their escape.
Sam, Max and Ruth make their own escape via hidden tunnels as the old dog attempts to figure out what they could be planning. Max decides to get back into her good graces by asking to help out. Permission granted, he starts looking for a weak brick, finds one, punches it and pulls out one of the inmates. When he refuses to talk, Ruth and Sam threaten to tell his mom, which causes him to spill the beans - the gang was going to tie up the guards while Hurtzog was going to hold the warden hostage. Satisfied, Ruth knocks him out with a nerve pinch.
The trio make their way through the sewers and into the showers; literally, as Ruth opens the faucet and it spits the three out. Sam is in awe of the place, though Max wishes they wouldn't say anything in disgust when Sam muses if the walls could talk. To trap the gang, the trio turn on every hot water faucet in the shower while Max reluctantly grabs the soap, a "Do Not Open Until X-Mas" sign placed on his rear end. When Hurtzog and his gang enter, they confront Ruth briefly before Sam and Max arrive with towels being whipped, frightening Hurtzog's goons into smashing into a heating grate. However, Hurtzog isn't fooled and makes his escape through the toilet, which Max does not want to go through. Instead, the trio follow through a hidden passage near a deadly fanblade.
In the warden's office, Hurtzog and his goons confront the warden after tying up his secretary and reveal they've also cut the phone lines. However, they're stopped as Sam and Max drops in, slamming into the goons and Ruth shows up, slapping a gun out of Hurtzog's hand and taking him out with a fruitcake. At that point, Santa Claus shows up from the nearby chimney and, making sure Sam and Max were good, delivers a bunch of gifts and bids them all farewell until next year. However, Hurtzog uses the opportunity to somehow recover enough to finally make his escape.
At a Christmas party, a teary-eyed warden notes how wonderful it is to see the other inmates so happy by Ruth's actions, he considers it a wonderful Christmas gift. Ruth, however, is more disappointed that Hurtzog escaped and wished she could have put him back. However, Max finds another gift aimed at her and Sam opens it, revealing a tied up Hurtzog. Everyone is confused as to how this could of happened as Max wonders if perhaps Santa did it...
"Christmas Bloody Christmas" was made available as part of Shout! Factory's Sam & Max: Freelance Police - The Complete Series DVD set.