at (someone's or something's) mercy
Under the control of or dictated by the actions of someone or something else, without the ability to defend or liberate oneself. When you're a minor, you're totally at your parents' mercy. When you travel by public transportation, you're always at the weather's mercy. Her fate is at the jury's mercy—it's their decision now.
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.