1. in secret秘密地，私下，暗地里，偷偷地

The meeting was held in secret.

会议是秘密召开的。

I was told about it in secret.

他们吧这件事秘密告诉了我。

He told me the news in secret.他悄悄地告诉我这个消息。

The miser buried his gold in secret and no one knows where it is.

守财奴把他的金子暗地里埋藏了起来，谁也不知道他的金子放在哪里。

Andrews had stashed money away in secret offshore bank accounts.

安德鲁斯已经将钱存到了秘密的海外银行账户中。

Dan found out that I had been meeting my ex-boyfriend in secret.

丹发现我一直在跟前男友偷偷见面。

Partisan fighters fought in secret against the enemy.

游击队战士神出鬼没地打击敌人。

She wept in secret.

她暗暗哭泣。

2. in the secret知道内情，知道这个秘密，参与秘密

She was in the secret from the beginning.

从一开头她就知道这个秘密。

I know a man who is in the secret.

我熟悉一个了解内情的人。

You must not take liberties because you are in the secret.

千万不要因为你知道内情就自作主张。

Is your brother in the secret?

你弟弟知道这个秘密吗？

Are you in the secret? 你知道内情吗?

Do you think it’s wise to let him into the secret?

你认为让他知道（参与）这个秘密是明智的吗？

另外：

keep sth. （a）secret from sb. 把某事对某人保密

He tried to keep it secret from his family.

这件事他试图瞒着家里。

I'm going to keep it a secret from everybody.

我要保守秘密，不让任何人知道。

I told her she didn't need to keep it a secret from me.

我告诉她不需要对我保密。

I can keep nothing a secret from you.

我对你没有保密的事。