happen on/upon sth/sb
literary词库：同义词和关联词
- a fishing expedition idiom
- alight
- ascertain
- break fresh/new ground idiom
- breakthrough
- catch sb red-handed idiom
- flush
- get wind of sth idiom
- happen
- have a (good) nose for sth idiom
- have got something there idiom
- hidden
- run sb/sth to ground idiom
- search
- search sth/sb out
- smell
- sniff sth out
- sniff sth/sb out
- stumble
- trace
