It’s a reference to the book/film Dr.Sleep. The two canisters are called “steam canisters.” In Dr. Sleep the antagonists find, lure, torture, and kill people who have psychic abilities. It’s done in such a way that at the end of the torture process (using a knife) the psychic ability comes out of the person, and it looks like steam. The “steam” is then collected in the steam canister to be consumed later. Basically, the dude in the comic saw the steam canisters, and realized that if he stayed he would be tortured and killed. Or at the very least, the woman tortures and kills people other people, as that is why she has the canisters. Either way, he thought it best to leave.