somebody's heart sinks
somebody's spirits sink

His heart sank, and he did not know what to do.

Though I already knew what he held, my heart sank.

Her heart sank, but she tried not to let him see.

His heart sank for a moment, then he saw the mark on the back wall.

Two children came out of the house and my heart sank.

Then he could see the lot better, and his heart sank.

My heart sank when I heard him say he was in full support of the government's policy.

He turned around quickly at the sound of his name, and her heart sank even further to see what had happened to him.

She looked out over the town and her heart sank.

She looked into those eyes now and her heart sank.