step in
  走進,進入;介入,干涉
  step in
       v 1: get involved, so as to alter or hinder an action, or through
            force or threat of force; "Why did the U.S. not
            intervene earlier in WW II?" [syn: intervene, interfere,
             interpose]
       2: act as a substitute; "She stood in for the soprano who
          suffered from a cold" [syn: substitute, deputize, deputise]