He has made dreadful mistakes before but not quite this obvious.

Now under house arrest, she says it's all a dreadful mistake.

Despite his firm statement on the beach, Laura knew that this was all a dreadful mistake.

They obviously don't mean anything to you, so it looks increasingly as if this whole business must have been a dreadful mistake.

Had she made a dreadful mistake by agreeing to help him?

After several hours, he was beginning to panic, fearing that he'd made a dreadful mistake.

He showed up seconds after my dreadful mistake was discovered.

He saw the letter as a dreadful mistake, and decided it must go no further.

The moment the train pulled out, he knew he'd made a dreadful mistake.

Soon I discovered my dreadful mistake, and diarrhea took hold.