An unabridged collection spotlighting the best space operas, alternate histories, and time travel stories published in 2021 by current and emerging masters of the science fiction genre, edited by Allan Kaster. "The Station of the Twelfth" by Chaz Brenchley-A stop along the monorail that loops around Cassini Crater pays tribute to the British heroes of a battle that took place on a Martian moon. "Mulberry and Owl" by Aliette de Bodard-In this Xuya story, a rebel on the run from the Dragon Throne pursues the decommissioned conscious ship that once hunted her. "Sleep and the Soul" by Greg Egan-In an alternate 19th century America, where humans do not sleep, all forms of unconsciousness are considered equivalent to death. "Re: Bubble 476" by A. T. Greenblatt-Time aberrations distort the communications sent between two close friends working in different bubble universes. "The Dark Side" by John Kessel-President McKinley's assassin becomes ever more delirious after taking a ride at the 1901 World's Fair inspired by H. G. Wells's First Men in the Moon. "Antonia and the Stranger Who Came to Rancho Los Feliz" by Lisa Morton- A man from an alternate L.A. uses a temporal portal to visit a ranch in a 20th century agrarian Los Angeles, in the nation of Alta California. "A Rocket for Dimitrios" by Ray Nayler-After salvaging technology from the wreckage of an alien saucer in 1938, the Americans are racing the Russians to find a second possible crash site in the aftermath of World War II. "Dream Atlas" by Michael Swanwick-A scientist discovers a dream continuum that stretches through space and time making it possible to observe the past and future. "The Burning Girl" by Carrie Vaughn-People with supernatural powers join William the Conqueror in an attack on the final stronghold of the last Saxon lords of England. "A Pall of Moondust" by Nick Wood- A botanist balks at returning to the lunar surface after surviving a freak accident on the Moon.