At the time of his death in 2018, at just 48, Icelandic composer Jóhann Jóhannsson left his sci-fi film Last and First Men unfinished. Now completed by friend and fellow composer Yair Elazar Glotman, the 70-minute movie unites atmospheric shots of former Yugoslavia’s “Spomeniks”—mysterious Cold War monuments to the Soviet country’s fallen—with passages from Olaf Stapledon’s 1930 novel that gives its name to the film. Jóhannsson’s underlying soundtrack conjures vast horizons and the stretch of billions of years with keening strings and vocals, haunting effects, and dusky textures. Each track moves in and out of being, from the menacing “Architecture” to the awe-inspiring “The Navigators” and an “Epilogue” that stutters and fades into eternity.