It looks like you're referring to — but a quick check shows that Season 5 actually has 12 episodes , and Episode 11 is titled "Journeycake" (not H255). "H255" doesn't match standard episode codes for Outlander .
Synopsis: As the drums of the coming Revolution grow louder on the Ridge, Claire and Jamie find themselves caught between loyalty to the Crown and the rising tide of rebellion. When a mysterious stranger arrives with a coded message marked “H255” — a long-buried Fraser prophecy tied to the stone circles — Claire realizes the key to altering history may lie in a sacrifice she never anticipated. Jamie must choose between protecting his family and leading his tenants into an uncertain war. Meanwhile, Roger and Brianna uncover a 20th-century clue that suggests the prophecy is not just about the past… but their children’s future. outlander s05 h255
