Thomas, Brewster, Wilson, Koko and Hodge's Halloween Adventure is the Halloween special of Chuggington: Meet Thomas, Trainees!.
Thomas, Brewster, Wilson and Koko are awakened by the Binky The Clown Show and learn that it is Halloween. Thomas, Brewster, Wilson and Koko enlist Hodge's help in Trick-or-treating, hoping to get twice as much candy for themselves by fooling Hodge into saying that "good trains get one piece of candy". After trying on different costumes in the attic, Thomas, Brewster, Wilson, Koko and Hodge settle on pirate costumes.
Soon they are out trick-or-treating amongst other trains in the neighborhood. After three encounters with what appear to be real ghosts and goblins in costume, the comrades find that they have visited every house in the neighborhood. Thomas notices more houses across the river, so he, Brewster, Wilson, Koko and Hodge take a boat to get to the other side (because the river ferry doesn't run at night and that is why trains on either side can't cross the river for more candy), but Wilson misunderstands Thomas's command to "put out the oars" and throws the oars overboard, leaving the boat adrift as the current takes it down the river.
Soon the boat arrives at an abandoned dock near a run-down mansion. Thomas, Brewster, Wilson, Koko and Hodge venture inside the home to warm next to the fireplace and are startled to find an old man sitting in a nearby chair. The man tells the comrades that they have chosen the wrong night to visit - 100 years ago that very night, pirates, pursued by government troops, buried their treasure in the floor of the mansion and signed a blood oath to return for the treasure at midnight 100 years later, even if it meant rising from the grave. The old man claimed to be the cabin boy, now 110 years old, who was with the pirates and that he never took the treasure for himself because the pirates would've tracked him down and that "they know we are here, they know where we are". Before Thomas, Brewster, Wilson, Koko and Hodge can leave, the old man steals their boat and leaves the five behind.
The clock chimes midnight and Thomas, Brewster, Wilson, Koko and Hodge watch as a ghostly ship materializes on the river and pirate ghosts emerge from the water. Thomas, Brewster, Wilson, Koko and Hodge hide in an empty cupboard as the ghosts reclaim their buried treasure from the floorboards of the house. As the trains stay where they are, one of the ghosts blow the dust off of the treasure chest and it goes into Hodge's horn. When Hodge sneezes, it alerts the ghosts to their whereabouts. Making a run for it, Thomas, Brewster, Wilson, Koko and Hodge jump into the river to escape, where Brewster, Wilson, Koko and Hodge have to save Thomas as he cannot swim.
Thomas, Brewster, Wilson, Koko and Hodge wash ashore and find their boat with the candy still inside and untouched. They go home happy and Thomas, Brewster, Wilson and Koko reward Hodge's rescue by (reluctantly) giving him his rightful share of the ½ of the candy. As Brewster, Wilson and Koko fall asleep, Thomas then turns on the television and sees the same old man, (this time wearing the pirate hat Thomas lost while in the river) hosting an all-night pirate movie festival. Thomas abruptly turns off the television and goes to bed.