"How could all of this have been kept secret for so long?"

"But I have never kept anything secret from my husband!"

"Bad news is something that should be kept secret and never told."

News of this sort could not be kept secret for long.

First, this should not be kept secret, even for a limited time.

"You understand why this news must be kept secret for the next several hours?"

They wanted them to be kept secret for various reasons.

Because they would learn what she'd kept secret all these years, then come asking questions.

Some things will only be kept secret until a certain time.

Some things need to be kept secret for security reasons.

Thus he is able to live under water, but must keep his secret from the world.

They had been able to keep their dark secret to themselves.

At first, they had made every effort to keep their secret to themselves.

She kept her secret until the end of the game.

So we're going to keep a few things a little secret.

And they would have to be kept a secret from everyone until then.

Three may keep a secret, if two of them are dead.

The plan works, although she is told to keep her services a secret.

Each was told to keep the news a secret from the others.

Two can keep a secret, if one of them is dead.