In The Kid Detective (2020) When the detective was sure that the paper folding received by Caroline is the same as what Gracie had(made?), why did he suspect principal Erwin and go to investigate his house?
When Abe is told that the person accused of stealing the fundraiser money was actually innocent he begins to suspect that that person was set up.
He then realises that only someone with access to the lockers could place the origami flowers in Caroline's locker. He recalls that all students were required to give their locker codes to the principal's office.
Since Gracie was also receiving the flowers it must have been someone who was at the school all the time which leads him to think of the Principal.
So Abe breaks into the Principal's house to check out his theory and finds a picture stolen from the murdered boy (Patrick).