i-know
Explanation
This comic is a single-panel Halloween joke. A small trick-or-treating girl wearing a "Ghost" t-shirt stands at the door of an older man. Instead of the usual "trick or treat" routine, she says: "I know what you did. I know about the 'accident.' Trick or treat."
The caption below reads: "The odds were low, but if it worked, the payoff would be legendary."
The joke is about a child employing a blackmail strategy at random — going door to door implying she knows about some dark secret in each homeowner's past. The humor lies in the absurd gamble: most people would just be confused, but statistically, eventually she'd knock on the door of someone who actually did have a guilty secret, and that person would presumably shower her with candy to keep her quiet. It's a playful riff on the "cold reading" technique used by con artists and fake psychics, applied to the innocent context of trick-or-treating. The scare quotes around "accident" are the perfect touch, implying something sinister enough to provoke guilt in the right target.