Pipeline: a Novelette - The Mommy Mysteries, #6

When the Jones brothers beg for a sleep-over with a friend from school, Mac doesn't see a mysterious plot unfolding. She sees the opportunity to watch a movie away from her kids' prying eyes. Mac doesn't know the sleepover guest is smuggling something vile into the house, and he won't be taking it with him when he leaves. As a ferocious beast tears her home to shreds, Mac is forced to discover the true identity of a hideous doppelganger, track the savage creature taking up residence in the bathroom, and take cupcakes to school.