War Against Fuse
Grandpa Max is nowhere to be found in the Future.
He was at Mt. Neverest to congratulate the player on their graduation.
The PastTo help fight the Fusion invasion, Max is lending all of his Plumber knowledge to aid Dexter and Professor Utonium in learning more about Planet Fusion and its inhabitants. Thus Max is currently working on a satellite to survey and spy on Planet Fusion. Fuse is all too aware of this plot, and constantly sends his forces to sabotage Max's project.
Anur Phaetos Saga
While retrieving a battery needed for the satellite, Max not only finds the negative battery missing, but he also finds out that Ben's old evil alien form, Ghostfreak, and his people, the Ectonurites, are involved with Fuse after he spared their planet, Anur Phaetos, a long time ago. In return for his mercy, the Ectonurites have promised to aid Fuse in his plot to invade Earth. To defend Earth from this possible secondary invasion, Max has set up a field that will alert him if an Ectonurite does decide to land on Earth.
Grandpa Max is stationed alongside Numbuh One and The Scotsman in the ruins of Townsville Park In the original game, he was also located in Ship's interior giving the Rath Nano mission, "Let Me Tell You About Rath!" He studies the giant Fissure torn in the middle of the park which is the area's Infected Zone. He suspects that Fuse is trying to awaken an ancient beast lying deep inside the Fissure. Many of Max's missions involve travelling into the Infected Zone to impede Fuse's efforts. It was mentioned he is good friends with Plumber Nathan and Plumber Carol.