Archie and Reddie are having a sleepover! That means they get to play super fun games all night long and wear their favorite pajamas! And even when a storm knocks out the power, they don't get scared. Well, maybe a little at first, so it's a good thing they have their trusty flashlights! But when Archie is woken in the middle of the night by a loud grumble, he's afraid there might be a monster in the house. Luckily, Reddie is there to remind him of his bravery as the two friends investigate together. Everywhere they look, the noise seems to follow, but they can't seem to find a monster anywhere. Is it super-sneaky, or could there be something else causing these late-night grumbles?