勇气游戏 Chicken

　　Mick and Kev, teen Irish lads, are at the shore, throwing rocks at empty cans, drinking cider. Mick's the pushy one, engaging Kev in a game of mumbly peg, his hand on top of Kev's, fingers splayed. As Mick moves the knife between their fingers, a train is heard approaching. What's Mick's purpose?