hit pay dirt

Calico Joeにビーンボールを投げつけ、Joeの選手生命を奪った元投手であった父親から、あのビーンボールは意図的であったという真実を引き出すために色々と昔の話を聞き出しています。
We've touched briefly on his marriages, one subject I had planned to avoid. After he takes a nap, I hit pay dirt with a simple question: "Did you ever play baseball in Arkansas?"
"Oh yes, in the Texas League we played the Arkansas Travelers several times a year. A wonderful old stadium in downtown Little Rok. Nice crowds."
The door swings wide open, and Warren springs to life. Forgotten games, old teammates, strange happenings, locker room humor, curfew violations, life in the bus leagues--we stay on the subject of minor-league baseball for a lot of miles.
野球の話とは言え、上の "hit pay dirt" は野球のヒットではないですね。
・McGraw-Hill Dictionary of American Idioms and Phrasal Verbs: Fig. to discover something of value. (Alludes to discovering valuable ore.) Sally tried a number of different jobs until she hit pay dirt. I tried to borrow money from a lot of different people. They all said no. Then when I went to the bank, I hit pay dirt.
・Cambridge Idioms Dictionary: to achieve or discover something important or valuable She finally hit pay dirt with her third novel which quickly became a best seller.
宝物を掘り出した感じですね。