To leave someone in the lurch means not to help someone in a difficult situation. It can also mean or to abandon someone or put them in a difficult or impossible situation. This expression is similar to 'leave high and dry' or to be 'in dire straights'.

1. Helen just moved out without warning, totally leaving me in the lurch. Now I'm going to have to cover her share of the rent and bills for this month.
2. My car broke down in the middle of the motorway at night and when I called for assistance I was told they couldn't help. I was completely left in the lurch.

1. John quit just before his shift was about to start. He has really left us in the lurch!
2. After everything my boss has done for me, I just couldn't leave her in the lurch. That's why I turned down the job I was offered by another company.