Behind closed doors phrase
If something is done behind closed doors, it is done privately or secretly, or with no audience or crowd watching
I don't care about what is happening behind closed doors. It's none of my business.
A: Lisa and Andy have just got divorced. I thought they were an absolutely perfect family. B: You never know what happens behind closed doors.
They are negotiating the contract behind closed doors.
I'm afraid that the UEFA Euro 2020 will be held behind closed doors because of the Covid-19 outbreak.
Used to tell someone to keep secret what you're about to say
The room you are currently in.
To be secretly working together
When two individuals desire to be alone with each other, a third person is not welcome.
The phrase is hyphenated when being used before a noun.
They held a behind-closed-doors conference.
Used to allude that the last force, problem or burden which is seemingly minor and small causes a person, system or organisation to collapse or fail
Her husband's violent act last night was the straw that broke the donkey's back and she left him