Focus Features has acquired movie rights to the Robert Silverberg sci-fi story “How It Was When the Past Went Away.”

Producers are Wyck Godfrey and Marty Bowen of Temple Hill Entertainment, producers of the “Twilight” franchise. Vince Gerardis is executive producing.

The Pastor brothers, David and Alex, are adapting.

The movie is about what happens when everyone in a city suffers a mass/communal memory loss.

Silverberg’s short story centered on a lunatic putting amnesia drugs into San Francisco’s water supply with the city falling apart as people forget who they are, who they’re married to and where they work.

Isaac Klausner of Temple Hill developed the story with the Pastor brothers. Jeb Brody and Josh McGlaughlin brought the project in for Focus.

Temple Hill produced young-adult drama “The Fault in Our Stars,” starring Shailene Woodley, with a release date of June 6 from Fox.

Focus is releasing Tarsem Singh’s sci-fi thriller “Selfless,” written by the Pastor brothers, on Feb. 27.

Silverberg is a prolific sci-writer who published his first story, “Revolt on Alpha C,” in 1955.

The Pastors are repped by WME, Kaplan-Perrone and attorney Karl Austen of  Jackoway Tyerman Wertheimer Austen Mandelbaum Morris & Klein.