EXCLUSIVE: John Gallagher Jr. is boarding Amblin Partners and the Picture Company’s Larrywhich is based on the horror short by Jacob Chase. As Deadline broke exclusively in February, Chase will also write and direct the feature film.

Gallagher Jr. joins Gillian Jacobs and Azhy Robertson, who’ve already been set for the pic, which follows a young boy and his family who become the target of a monster who materializes through electronic devices. The Picture Company’s Alex Heineman and Andrew Rona are producing.

Gallagher Jr. will next star in Will Eubank’s Underwater opposite Kristen Stewart for 20th Century Fox and The Best of Enemies opposite Taraji P. Henson and Sam Rockwell for STXfilms. Recently, he appeared in The Miseducation of Cameron Post opposite Chloë Grace Moretz, which premiered and won the Grand Jury Prize at this year’s Sundance Film Festival. He is also starring in Amazon’s  just-announced half-hour romantic comedy anthology Modern Love alongside Anne Hathaway, Tina Fey and Dev Patel; directed by Emmy Rossum. Other credits include STXfilms’ Peppermint, Paramount/Bad Robot’s 10 Cloverfield Lane as well as Aaron Sorkin’s Emmy-winning HBO drama series The Newsroom.

Gallagher Jr. is represented by UTA, Wetzel Entertainment Group and Morris Yorn.