Calamity Jane saves Lucky Luke from a delicate situation. A friendship is quickly formed, and they arrive together in El Plomo... where Calamity Jane proves by her manners and her strength that she's not a weak woman: She acquires the local saloon by winning an arm-wrestling match! Its ex-owner, August Oyster, is hopping mad and has only one obsession: to send her packing. During this time, Lucky Luke tries to clear up a dark affair involving arms traffic...