It was on his way back past them, clutching a large doughnut in a bag, that he caught a few words of what they were saying。
这句话为什么第一句会有俩个动词，我原本想的是可能是past them作的句子后置主语，但是又不像。另外那个第三句的that也不知道是作什么成分。望指教！