1.hit-and-miss 碰巧的
2.pin sb down 按住，使动弹不得
Two men pinned him down until the police arrived.
3.hot on sb trail 快要抓到，即将找到
4.game of cat and mouse 猫捉老鼠游戏
5.track sb down 搜寻到，追踪到
The police have so far failed to track down the attacker.
