After reuniting with Heath and Tara on The Walking Dead in "Swear," fans quickly lost track of Heath again when he vanished early on in the episode. After two weeks of scavenging, a walker-infested bridge forced Heath and Tara to separate, after which the show followed her journey while leaving his up in the air. When Tara returned to the last place she saw Heath, the clues about where he'd gone were few and mostly frustrating. Their RV was gone, his glasses were crushed on the ground, and there was a white keycard with a potential message scrawled on it: "PPP." But what does "PPP" mean on The Walking Dead?
This mystery is definitely one of the more opaque ones. It's impossible to say if the letters or card were even left by Heath, though Tara is hopeful that that is the case since it would mean he's still alive. There are no immediate answers as to what "PPP" could mean and the only one who knows the answer is executive producer Scott Gimple — and as per usual, he's not telling. Perhaps Heath and Tara passed those two weeks playing the iconic board game Pretty Pretty Princess, and it's a shoutout to their favorite hobby. Maybe it's a failed attempt at a post-apocalyptic emoji. It could also actually be "ddd," or even some poorly illustrated music notes. There's really no way to know yet, but that doesn't mean fans aren't guessing.
There are, of course, endless random guesses that probably have no relevance to The Walking Dead. "PPP" is a symbol used when reading music that indicates intensity or volume; it's short for pianississimo, which means volume that would be very, very soft. Some fans are taking this as a reference to an upcoming threat from the comics, a group called the Whisperers. But if that's the case, it's fairly obscure. "PPP" could also be like Enid's JSS (just survive somehow) or Morgan's arrows: it could act as a signature, or breadcrumbs intended to lead Tara to Heath's location. If so, she didn't do a great job of following them.
But maybe Heath didn't leave the keycard at all. It could have been dropped by whoever took him, if a group did, in fact, take him. Characters have been abducted before, so it's definitely plausible that Heath was grabbed by another group — maybe even the group that's been torturing everyone all season long, the Saviors. The Saviors have been shown to code things with letters, like the A on Daryl's sweatshirt, so "PPP" could mean something to them that hasn't been revealed to the audience yet.
A Youtube video by CG27 posits that "PPP" stands for Potomac Power Plant, an abandoned power plant close to Alexandria. While the video theorizes that it's a power plant that belongs to Alexandria where Heath is lying low, it's also a possibility that it's another Savior outpost. The Saviors appear to live mostly in buildings like that: the satellite station that the Alexandrians attacked is one, and the Sanctuary is also an old factory.
Seeing the message again will hopefully bring some clarity to the situation, because right now those P's might as well be giant question marks. Hopefully the series will clue us in soon enough.