The circus has finally arrived in Green Lawn! Bradley, Brian, Nate, and Lucy are thrilled to see the big tents going up in their town. Unfortunately, the performers are having a terrible time getting the show ready. Equipment is broken, acts are a mess, and the whole event is on the verge of being canceled. The four friends happily volunteer to help the crew fix everything before opening night. They manage to get the stage ready, but the circus is still missing its most important act: a daring acrobat to swing on the high trapeze! Out of nowhere, a mysterious performer wearing a mask steps up and completely dazzles the crowd with amazing flips and tricks in the air. Everyone wants to know the secret identity of the incredible masked flyer. The kids realize they have a brand new mystery to solve right under the big top! Follow along as they search the circus grounds for clues and try to unmask the talented star. Can you help them figure out who is hiding behind the disguise before the circus leaves town? Step right up and join the investigation!