To turn to somebody is to go to them for help when you are in trouble. There is nobody else, and there they are.
It is one of the warmest phrases in English, and having nobody to turn to is one of the bleakest. It also works with things rather than people, since turning to drink is a well-worn phrase for a bad answer to a problem. There is a plain sense of changing to a page, and a sense of becoming, since milk turns to cheese and rain turns to snow.
Practised in Phrasal Verbs, A Man Called Ove
First appears in chapter 3 of A Man Called Ove.
Practise this word