When you have a ghost as your friend, like Tom Golden does, you quickly learn the benefits. Grey Arthur supplies Tom with pens in class, grabs Tom's lunch when he forgets it, and generally helps him out as any best friend would. It's just that, in this case, no one else can see Grey.
But right as Tom is settling into a comfortable routine, his life is once again turned on its ear when Grey Arthur starts a school for Invisible Friends in Tom's house. Ghosts are crowding into Tom's room and setting up camp in his attic with hopes of learning the art of the newest job in the ghost world. Meanwhile, other ghosts are mysteriously disappearing, and the repercussions are felt throughout the human world, even by Tom's parents. There are sinister forces at play, and it's up to Tom and Grey to figure out what's going on.