Harry scores high on Ernie's IQ test, which changes the way everyone relates to Ernie especially when his teacher Ms. Hall comes to visit and encounters Harry.
Brett thinks a primitive mask can cure his ailing love life by casting a spell on Darcy's Swedish au pair Uma, and it seems to work; but his date with her is spoiled by Harry, who is strangely obsessed with the mask as well.
It's Halloween and Harry finally has a chance to get out. However, the Hendersons' neighbour, who is allergic to animal hair, becomes suspicious of Harry's "costume."
While on a camping trip with his son and his co-worker, George is nervous because his co-worker keeps on playing pranks and later mistakes Harry for a monster.