The detectives 'dug into' his past and learned that he had once lived in another country.
Her fingernails 'dug into' my hand. = She 'dug' her fingernails 'into' my hand.
The salesman 'dug in his heels' and refused to lower the price any further.
(..) she saw something in it. It was a bag of gold. All right. The king had put that rock in the road because he knew the person who dug it out, who did something, they deserved a reward. They deserved to have their life changed for the good.... forever. I invite you all to sup with us (..)2017 TvShow: The Walking Dead Title: Rock in the Road Season: 7 Episode 9
(..) They were hungry. They didn't have any money. She just... sat there and cried, but... ...she wondered why it was still there... for it to hurt someone else. So she dug at that rock in the road with her hands till they bled, used everything she had to pull it out. It took hours. And then... (..)2017 TvShow: The Walking Dead Title: Rock in the Road Season: 7 Episode 9