It's based on a true story, though in tracing how the vibrator (ahem) rose to prominence, it's pitched mainly as a romp.
Hugh Dancy plays Mortimer, an idealistic doctor in 1880s London who, under the tutelage of Dr Dalrymple (Jonathan Pryce), treats female patients for "hysteria" by administering manual relief. When he starts to suffer hand cramps, his aristocratic inventor friend (Rupert Everett) stumbles on a solution: a mechanical instrument to give the ladies what they want.
Maggie Gyllenhaal and Felicity Jones play Pryce's daughters and Sheridan Smith plays a prostitute-turned-housemaid nicknamed Molly the Lolly ("Fancy a lick?").
It's that sort of film, deriding old-school myths of sexuality while playing up a seaside-postcard humour not seen since the days of Carry On.