Kilt-wearing American Elmo McElroy (Samuel L. Jackson), an illegal drug chemist, travels to Liverpool hoping to find a market for his new designer drug (which is supposed to be 51 times more effective than cocaine, hence the title) after double-crossing drug dealer The Lizard (Meat Loaf) back in L.A. This is McElroy's last big deal before he retires, and he plans to sell the drug to another crime boss Durant (Ricky Tomlinson) for $20 million, but his chaperone and guide to the Liverpool rave scene is local scouse gangster and rabid xenophobe Felix De Souza (Robert Carlyle).
Things go awry and soon McElroy finds himself on the run in the company of Felix, who really just wants tickets to the Liverpool F.C. versus Manchester United football match. Hot on their heels is female assassin Dakota (Emily Mortimer), who just happens to be Felix's ex-girlfriend, and crooked cop Kane (Sean Pertwee). McElroy and Felix try to do business with big-time Merseyside dealer Iki (Rhys Ifans), while all the while trying to avoid their pursuers.