"I heard you talking about the tree," Aunt Selby said. "Remember, I told you I have a Christmas tree somewhere in the house," Selby said. "I wanted to tell you where it was, but I haven't put it up the last few years. So I've forgotten where it was. You are welcome to look for it. I made it when Seymour died, and I've used it every year. It's made out of macaroni."
When the Callister family from Christmas at the M&M are reunited with their father right before Christmas, the first thing they want to do is buy a Christmas tree. Before they can buy one, they are called to the home of their elderly aunt, Selby Blue.
Aunt Selby asks the family to move in and take care of her. The children are ecstatic at the thought of living in the run-down mansion, but are shocked to hear that Selby Blue is allergic to pine needles and they can't get a Christmas tree. She tells the children that if they can find it, they can use a tree she had made out of macaroni.
As the children search for the tree, Aunt Veronica arrives, demanding that the mansion should be hers. With angry aunts, a cousin who eats all of the Christmas cookies, and a ghost in the attic, will it be the Callister's merriest Christmas ever, or the craziest? The "Macaroni Christmas Tree" just might hold the key.