leave someone in the lurch

Kazuo Ishiguroの短編MALVERN HILLSの主人公は姉夫婦のカフェーの手伝いをしていますが、無給なので忙しいと逃げて作曲に取り掛かったりします。
I came down off the window sill, put away the guitar, and threw myself down on my mattress. Then for the next little while I stared at the pattern on the ceiling. It seemed clear I'd been invited here on false pretences, that this had all been about getting cheap help for the busy season, a mug they didn't even have to pay. And my sister didn't understand what I was trying to achieve any better than did her moron of a husband. It would serve them both right if I left them here in the lurch and went back to London.
"in the lurch" は知らない表現ですが、文脈からすると、「突然」あるいは「黙ってそっと」でしょうか？　辞書で確認します。
i・American Heritage Dictionary: in the lurch: In a difficult or embarrassing position.
私の勘ははずれですね。他の辞書をよく見ると "leave someone in the lurch" で次ぎの説明がありました。
・Macmillan Dictionary: leave someone in the lurch: to leave someone in a difficult situation without helping them
・Collins English Dictionary: to desert someone in trouble: To leave someone in the lurch, just like all those Enron employees.