Harvey Weinstein and his brother, Bob Weinstein, will have a showdown Tuesday that will inevitably lead to screaming, profanities and ultimately the threat of a lawsuit that could do in the company ... multiple sources connected to the meeting tell TMZ.

The Board of Directors of The Weinstein Co. has a meeting on the books and we're told Harvey Weinstein's firing is on the agenda. Harvey will be on speakerphone ... he's in Arizona to get treatment for behavioral issues and sex addition. His civil lawyer, Patty Glaser, will be present in the room.

Our sources say Glaser is prepared to outline multiple reasons why her client's firing violates his contract. As we reported, the company never gave him a reason for booting him out, and our sources say to this day the company has never offered Harvey or Glaser any reason. She's also prepared to argue Harvey did not violate the contract.

As we reported, there's a provision that covers claims such as sexual harassment, and as long as Weinstein reimburses the company for any settlement or judge and then pays a penalty, all is good. Glaser will note the contract was signed in October 2015 and since then there hasn't been a single claim against her client.

As strong as Glaser is, we're told the lawyers who rep TWC, O'Melveny and Myers, believe the company had every right to fire Harvey. They say the company's Code of Conduct gives them that right, but we're told Glaser's position is that the contract trumps the Code.

Now the heat ... our sources say Bob Weinstein is angry -- livid -- over the whole situation and loses control during heated conversations. Harvey and Bob are birds of a feather, and people involved in the meeting say it's inevitable things will get loud and ugly.

We're told Glaser is ready to amp things up if the Board doesn't see things her way ... which is unlikely. She can try and force mediation and arbitration, which is provided for in the contract, but if the Board won't play ball we're told she's ready to file a lawsuit.

As one very connected source put it, "There is so much crap that will be unearthed in a lawsuit, the company just can't survive it."