Rookie police officer Chase McCain is assigned by Deputy Dunby to investigate a missing pet. After interviewing the distraught pet owner, McCain meets Doorlock Homes, who teaches McCain how to look for clues using Detective Points.
McCain and Homes find the dog's bone and then a shirt with a label indicating it belongs to the Knuckles Gang. Homes finds an address on the label, and McCain goes to investigate. Finding the gate locked, he climbs the roof of a neighbor's house and uses his scanner to listen for sounds. Identifying a barking dog, he rides a zipline to the house. He then climbs a drainpipe and eventually reaches the balcony where the dog is being kept in a crate.
McCain returns Mr. Waggles to his happy owner. Deputy Dunby then grumpily calls McCain back to the LEGO City Police Station.