Marilyn Monroe is a magnetic misfit in Speculations, a spicy conspiracy drama full of bombshells

A smartly dressed woman hammers away at an old-style typewriter in a drawing room. She is the real-life American journalist and conspiracy theorist Dorothy Kilgallen (Janie Dee) and bears the gimlet-eyed look of Angela Lansbury in Murder, She Wrote.

Torben Betts’s play could be called Marilyn, She Wrote. It is the 1960s, Marilyn Monroe has been found dead in her bed and Kilgallen thinks both John F Kennedy and his brother Robert F Kennedy (Jolyon Coy) had something to do with it. Her investigations form part of an unpublished book which suggests links between a political cover-up and underworld crime that, she argues, led to Monroe’s death aged 36.

Kilgallen receives a threatening phone call from a stalker just as the babysitter, Flo (Gloria Obianyo), arrives. She confides in Flo and the play is shaped around their conversations, which snap to slickly enacted flashbacks of Monroe (Natalie Dunne) in her bedroom with RFK, as well as scenes of JFK’s killer, Lee Harvey Oswald (Joseph Potter), in a bar with criminal mastermind Carlos Marcello (Ferdy Roberts).

It helps that Flo is a wannabe journalist, whom Kilgallen instantly takes under her wing, and that she is African American, so sees the Kennedys as vital forces for good in the civil rights movement. But it is still too convenient a plot device that someone as shrewd as Kilgallen would explain all her theories to a complete stranger.

Director Trevor Nunn creates a smoothly oiled production nonetheless, eliciting strong performances from the cast which never seem like tacky imitations. The standout highlight is Dunne. Monroe has been played so many times that any portrayal runs the risk of cliched impersonation but Dunne is variously dishevelled, vulnerable, angry and unglamorous yet able to turn on the allure. At her most upset she appears like Monroe in her exposing final performance in The Misfits.

Lee Newby’s set design does its own transformative thing, rotating elegantly between timeframes. But all the machinery seems to try too hard to paste over the play’s limitations. It feels static as people talk out their theories and grudges.

As far as Monroe conspiracy theories go, Kilgallen’s was surely explosive then but has little new in it now. The less familiar bit here is Oswald’s connection to Marcello and Oswald’s own assassin, Jack Ruby, as well as questions around the death of Kilgallen herself in 1965, which this play leaves abruptly hanging. One speculation too few?