A found-footage film (oh no) but improved by the sci-fi aspect. Thomasina “Tom” and Martha “Mars” are happy with their time-television, dancing to David Bowie in 1940. Military agent Sebastian locates and joins them after they start broadcasting warnings about near-future nazi bombings, and inevitably one girl (Mars) falls for him. Some cute multiverse moments: they sing “You Really Got Me” and a ragtime version becomes the theme song and slogan of the war effort. But the girls aren’t great war strategists and botch a couple important things leading to (in order of increasing horror): the USA dropping support for Britain, the nazis winning the war, and erasure of David Bowie’s career. No longer trusted by anyone, the back half of the movie is all running around spy/escape scenes. Mars shooting nazis while hanging from a noose isn’t the movie’s strong suit, the early cross-timeline TV stuff is. Finally they leave messages from their alt-present to their unspoiled past selves and manage to undo the damage.
Tom (the serious, dark-haired sister, whose large eyes get put to good use) is also in a netflix fantasy show, Mars in that horrorish movie Make Up, and Seb in that movie about the Bronte sisters.