There is a new family in town, and they are giving all the kids at Odyssey Elementary the creeps — especially Jack and Lucy. They have to walk by the family's house every day, and Lucy is spooked by the young boy she sees staring at them through the window. At school, they hear further rumors about the family from Alice Pringle. Alice's brother saw the strange family's father leaving the house early in the morning, carrying what looked like a big sack with a body in it. Jack deduces that the father is a Mafia scientist.

Later at Whit's End, Whit tells Jack and Lucy the name of the family: Kirban. Whit says they are very private people, which just makes Jack even more curious to find out about them. Lucy, on the other hand, wants nothing to do with the family. She even refuses to walk by the house with Jack the next morning. At school, Jack informs Lucy that the boy wasn’t in the window that morning. Just as Lucy wonders where the boy went, the teacher introduces a new student...John Kirban! No one even gets close to John all day, which makes Lucy feel guilty.

After school at Whit's End, Jack reveals plans to spy on the Kirbans and wants Lucy to help him. She refuses. Jack storms off angrily, bumping into Connie on the way. Connie talks to Whit and tells him that she saw John Kirban sitting on the curb by himself, crying. Whit goes to Lucy and asks her to do him a favor: walk to school the next morning with John Kirban! Lucy tries, but when she reaches the Kirban’s house, John's father nearly slams the door in her face, telling her that John isn't going back to school that day or any other.

Lucy runs from the house, terrified, and runs into Jack. He tells her not to worry — he's going to spy on the Kirbans that night and expose the whole Mafia/mad-scientist family! But thanks to a stray cat and several trash cans, it is Jack who winds up exposed — caught by Mr. Kirban! A police officer is summoned, and gets to the bottom of things. The bag the father carries out to his van contains... a carpet. Mr. Kirban is a carpet maker. The family seemed unfriendly and mysterious because they are from a different country. Jack is released back to his parents' custody, Whit decides to buy a new carpet, Lucy has a new friend in John Kirban, and everyone learns that you can’t always believe what you hear.