Nic Pizzolatto is on board to pen the script, while the 'Iron Man' actor is set to star.

Robert Downey Jr. may be on the list of feature stars turning (or in his case, returning) to the small screen.

The Iron Man star is teaming with True Detective creator Nic Pizzolatto for a drama at HBO. Details about the project are being kept under wraps and it's unclear if there are any official deals as of yet, but Pizzolatto will pen the script and Downey will star.

Sources say the project may be based on Downey's long-gestating Perry Mason reboot, which rather than a Warner Bros. Pictures feature is now being eyed for the small screen with Downey's wife and producing partner, Susan Downey of Team Downey, set to exec produce with the actor.

HBO declined comment.

For Downey, should the HBO project move forward, it would mark his return to the small screen following his role on Fox's Ally McBeal.

Pizzolatto, meanwhile, has an overall deal with HBO stemming from True Detective, with new HBO programming president Casey Bloys telling reporters July 30 that the anthology "is not dead." The pay cabler has Pizzolatto locked in through 2018, and Bloys revealed the writer does not have an idea for a third season but is "busy working on some other projects" at the moment — which might indicate his collaboration with Downey.

Downey and Pizzolatto are repped by CAA; the latter is additionally handled by Anonymous Content.