In April 2019 in Ellis, Columbia State, Grade 5 students Mitchell "Mitch" Carter, Mike Brock, and Morgan Lamb are walking to their treehouse in the woods nearby after school. As soon as they reach the main trail, they hear gunshots, and rush to find out what happened. When they get to the scene of the crime, they discover the body of Jeremy Diggins, an accountant with Eckstein's Goods who used to do forensic accounting in Alford, Pulford State. The three boys, who call themselves the 3 "M"igos, rush to get Detective Mack Evans of the Ellis Police Service, but when they return, the body's gone! Detective Evans and the officers with him are unimpressed, and leave in a huff of anger at the boys' "game." Mitch, Mike, and Morgan decide to take it upon themselves to solve the case. Will they get the cooperation of other adults in Ellis as they investigate? Will they be able to find Mr. Diggins' body again? And, most importantly, will they be able to get Detective Evans to believe that they were telling the truth, and enlist his help to solve the case?