Chris Geraghty Cast The Alienist TNT Teddy Roosevelt

Brian Geraghty Cast as Lead of TNT's The Alienist, Replacing Sean Astin

TNT’s upcoming detective drama The Alienist has found a new lead actor.

Chicago P.D. alum Brian Geraghty will replace Sean Astin in the lead role of future U.S. President Teddy Roosevelt, our sister site Deadline is reporting. “Unfortunately because of scheduling difficulties, Sean Astin will no longer play the role,” the network said in a statement.

Adapted from Caleb Carr’s bestseller, the crime thriller is set in 1896 New York, where a young Roosevelt, as the newly-named NYPD commissioner, is investigating a string of brutal murders involving boy prostitutes. He enlists an “alienist”/criminal psychologist (played by Daniel Brühl) and a newspaper illustrator (Luke Evans) to help solve the heinous crime. Dakota Fanning and Q’orianka Kilcher also star.

The drama, which got a straight-to-series order from TNT, is currently filming in Budapest, and with Astin also filming Season 2 of Netflix’s Stranger Things in Atlanta, Deadline says the amount of travel required to do both was too much to overcome.

Geraghty played cop Sean Roman for two seasons on Chicago P.D., wrapping up his run last May. His other TV credits include True Blood, Boardwalk Empire and Ray Donovan.