A boy called Theo wanted to make another kid, Marcus, look bad, so he faked a screenshot — he typed a mean message, made it look like it came from Marcus, and sent it round the group chat. It's not real; Marcus never said it. But it looks completely real, and people are believing it. Marcus is suddenly getting messages telling him he's horrible. Theo's friend Sam knows it's fake — he watched Theo make it. Marcus is confused and upset, defending himself against something he never said, and nobody believes him because "there's a screenshot." The fake is doing real damage. Sam is the one person, besides Theo, who knows the truth — and so far he's said nothing.