happen upon
verb1
To accidentally encounter a person or situation; to chance upon, happen on or stumble across.
- The old haunt that defines “Dragonstone” isn’t Dragonstone, though. It’s the house of that peasant father who took in the Hound and Arya, fed them, and gave them a good night’s sleep only to be robbed. In the present, the Brotherhood Without Banners happens upon the man’s house.2017 July 16, Brandon Nowalk, “Chickens and dragons come home to roost on Game Of Thrones (newbies)”, in The Onion AV Club: