(CNN)With the added bonus of dueling Mr. Darcys for "Pride and Prejudice" aficionados, "Operation Mincemeat" unites Colin Firth and Matthew Macfadyen in an extraordinary true story of World War II espionage, built around Winston Churchill's statement that in war, truth should be accompanied by "a bodyguard of lies." Here, the deception hinges on a corpse, with thousands of lives hanging in the balance.