Here is an overview of the game’s story, via its official website:
When the Monad Quantum Research Facility—30 miles off the shore of CA – is attacked by an unknown entity, engulfing the complex in flames and putting it into a full containment lock-down, a distress call is sent for mutual aid to the Garboa Fire Dept in San Francisco, California.
Fire Chief Sturgis answers the call and sends you—Captain Jacob Thomas—your partner Shane Costa and a crew by helicopter to the Monad Facility.
Your mission is simple: save as many lives from the burning complex as possible and get out. However, what starts as a rescue mission quickly plummets into darkness, when you arrive and find that things are not as they appear.
Watch the trailer below.
Update 03/26/21: Here is the full-length 18-minute version: