A minor character has a MacGuffin and is being pursued by some Mooks. They fatally wound the minor character, who then hands the MacGuffin over to the main character(s) before dying. The main character(s) continue the dead person's mission to get the MacGuffin to wherever it's supposed to get to before the bad guys get it. A good way to keep the true story a mystery (and to keep the audience interested) is to have the main character be an Unlikely Hero that has NO idea what's going on or who to trust. May be a Harbinger of Impending Doom. Contrast Come with Me If You Want to Live.