San Francisco is gripped by fear as a serial killer stalks the streets, leaving bodies - and baffling ciphers - in their wake. Each message is a taunt, splashed across headlines and police briefings, daring anyone to crack the code.
For Icky Taylor, a sharp-eyed, chronically bored office worker, the case is just another grim curiosity - something to follow during breaks. Until the police arrest a homeless man Icky knows, a gentle soul who couldn't hurt anyone, at the scene of the latest murder.
Digging into the ciphers, Icky spots what everyone else misses: the symbols aren't random. They're lifted from an obscure video game from the 1990s - one almost no one remembers. Almost.
Dismissed by the authorities and mocked online, Icky finds themself racing against time to prove the truth. But one thing becomes terrifyingly clear: the real killer knows Icky is getting close - and doesn't plan to let them finish the game.