Leave somebody in the lurch
Definition 1 of 1
Pro Tip 1/3Unexpected Timing
This phrase often implies that the abandonment happens at the worst possible time for the person affected. 
When the guide didn't show up, the tourists were left in the lurch at the start of the hike.
Pro Tip 2/3Emotional Impact
Use this phrase to express a sense of betrayal or letdown by someone who fails to fulfill their promises or duties. 
Sarah left me in the lurch by quitting right before the project's deadline.
Pro Tip 3/3Not for Emergencies
The phrase should not be used when someone can't help because of an emergency—it implies a lack of responsibility, not misfortune. 
He left us in the lurch because he went to a movie, not because his car broke down.