Director Drake Doremus envisioned Nicholas Hoult and Kristen Stewart as the leads, but only together and if either one of them were unable to do the film, neither would be in it.
In one scene, Silas has blood taken by a doctor. Nicholas Hoult had to wear a hospital gown during this scene to cover up a large bruise on his upper arm which he sustained while skateboarding with Kristen Stewart.
Filming took place in Tokyo, Japan and Singapore.
Kristen Stewart and Nicholas Hoult went skateboarding at 4am while on location during the shooting of the film to help develop the connection between their characters.
During one scene, Nia and Silas are seen sitting together on a wall while Nia reads something to Silas. Kristen Stewart is actually reading a poem she wrote during this scene.