The Mysterious House is a Halloween holiday special for The Walten Files. It was created similar to style of PSAs from the 70/80s, mostly telling children not to go into strangers' houses.
Summary
The Mysterious House tells us the story of Tammy and Duckie. One Halloween, Tammy and Duckie were Trick-or-Treating like most children do. As it got late, Duckie was ready to go home, but Tammy wanted to keep Trick-or-Treating. Tammy convinced Duckie to go to one more house, which led them to the Witch Sheep and the Pumpkin Rabbit's house. The Witch Sheep and the Pumpkin Rabbit mention that it's too dangerous for the children to walk home alone, with it being so late, and they ask them to spend the night, which Tammy and Duckie agree to.
Tammy wakes up in the middle of the night, and finds that Duckie is missing. She gets up and begins to look for him, encountering many creepy things. Eventually, she comes across a room, and there she finds the corpse of Duckie, along with the corpses of other victims from previous years. She then finds the Pumpkin Rabbit, who says that she shouldn't be wandering around so late. The video ends with the Pumpkin Rabbit having killed Tammy.