“顺藤摸瓜”，汉语成语，字面意思是“顺著瓜藤可以摸到瓜（follow the vine to get the melon）”，比喻按照某个线索查究事情，可以翻译为“track down somebody [something] by following clues”。

例句：

他们顺藤摸瓜，终于找到了罪犯的下落。

They tracked the criminal down by following clues on his whereabouts.