He was trying to keep the surprise a secret, but he accidentally let the cat out of the bag
She didn't want to spoil the ending, so she was careful not to let the cat out of the bag
The interviewer was very discreet, but the guest's slip-up let the cat out of the bag regarding the new project
Once the date of the wedding was announced, it seemed inevitable that someone would let the cat out of the bag
He tried to keep his plans secret, but his excited phone call let the cat out of the bag to his family
Hey, have you heard about the surprise party for Sarah?
Oh no, I totally forgot! Did someone already tell her? I really hope they didn't, or they'll have completely ruined it.
I'm not sure, but it seems like someone may have *let the cat out of the bag* with a few of her closest friends. Do you think we should still go ahead with the original plan?
He accidentally let the cat out of the bag about the surprise party
He revealed the secret about the surprise party unintentionally
The secret of the surprise party was accidentally disclosed by him