The Marilyn Conspiracy: a tawdry take on the starlet’s awful final days

There are some icons of the 20th century whom we simply refuse to allow to rest in peace and prime among them is Marilyn Monroe. She died at her California home in August 1962 at the age of 36; the verdict was “probable suicide”, but conspiracy theories have abounded ever since.

In this thriller-cum-whodunnit, Vicki McKellar and Guy Masterson sift through the details and discrepancies of the last four days of Norma Jeane Baker’s life, of how she went from a party on the Wednesday evening celebrating her new two-picture deal with Fox to, apparently, killing herself late on the Saturday.

Genevieve Gaunt, all breathy voice and capricious vulnerability, gives a convincing account of the fragile star with a penchant for pills and champagne. Marilyn is sexually involved with both (unseen) Kennedy brothers, Attorney General Bobby and President JFK, and there is immense consternation in Kennedy circles as to what career-detonating details Marilyn’s diary might contain and what, crucially, what she intends to do with it. McKellar and Masterson toggle between scenes involving Marilyn and those involving her seven-person inner circle in the hours immediately following her death. The most pressing question is this: why did it take them so long to call the police to report what had happened?

There is, initially, a whiff of tawdriness to Masterson’s production, which also threatens to be grindingly static despite a small central revolve. When the script veers into Agatha Christie territory, as Marilyn’s closest discuss timings and telephone calls in those all-important hours leading up to her death, there is a welcome injection of fresh impetus and interest. Movements and motivations – of her doctor, psychiatrist and housekeeper, not to mention actor friend Peter Lawford (Declan Bennett), brother-in-law- of the Kennedys – are carefully picked over, as well as pulled apart.

These scenes, for which we cannot help but expect Poirot to arrive like a deus ex machina to supply all the answers, have a mounting heft, as stories are offered and tweaked, to the horror of Marilyn’s loyal friend and publicist Pat Newcomb (robustly grounded work from Susie Amy). Stern housekeeper Mrs Murray (Sally Mortemore) remains fascinatingly unreadable, but all seven characters are loosely shackled to a merry-go-round of repeated gestures, interjections and exclamations, which a more refined script would have worked to avoid.

Marilyn aficionados won’t want to miss this and even those, and I count myself among them, who are immune to her boo-boo-be-do charms will find themselves increasingly intrigued.

Until July 27 (020 7870 6876, parktheatre.co.uk)