Time patrol

Hidden deep beneath the Metropolitan Museum of Art is the Time Patrol, a secret agency charged with protecting the world's timeline from the evil forces who wish to alter it. When the Patrol disappears without a trace, only twelve short hours are left before all life on Earth ceases to exist. Enter: the Nightstalkers. Summoned to find the Time Patrol, the Nightstalkers' elite covert operatives begin to notice rifts in their own worlds.