The pact was built into CBS‘ decision to greenlight the serialized drama from Steven Spielberg and Stephen King based on King’s novel for next summer. It establishes an in-season, online subscription-video-on-demand (SVOD) window for the show on Amazon’s Prime Instant Video service, which will become the exclusive online subscription home for Under The Dome.

Amazon Prime members will have unlimited streaming of all the series’ episodes four days after their initial broadcast on CBS. The unusual deal helps CBS offset the cost and was key for picking up an elaborate serialized drama for the off-season. There had been speculation that Under The Dome would be made available on Amazon after 24 episodes had aired. But Scott Koondel, Chief Corporate Content Licensing Officer for CBS Corp., explains the rationale behind the window’s length. “With this innovative agreement, we’re giving fans more options to watch and stay current with this serialized series, and doing so in a way that protects the Television Network’s C3 advertising window,” he said.

Last week, Amazon announced an exclusive online subscription deal for another scripted series, PBS’ hit Downton Abbey. Under The Dome is produced by CBS TV Studios in association Spielberg’s Amblin TV. Neal Baer, King, Justin Falvey, Darryl Frank, Stacey Snider, Jack Bender and Brian K. Vaughan, who wrote the television adaptation, serve as executive producers.  Niels Arden Oplev will direct the first episode. Casting for the series is currently under way.