It's rude to spy on your neighbors.
Jack suspects that his neighbor is stealing his mail every day.
Jack wants to get to the bottom of this.
Jack approaches his neighbor civilly and asks him if he knows what is going on with the mail lately.
Jack spies on his neighbor and sets up cameras to try to catch him in the act.
The neighbor reveals that the mail carrier sometimes mixes up addresses in this neighborhood, and just be patient.
Jack gets caught spying on his neighbor and then their interactions going forward are very awkward.