conspire with (someone) against (something or someone)

To join together in force or combine in such a way as to foil or defeat someone or something. I bet the CEO conspired with the head of HR against Tom. Why else would he have been removed from the company like that? The president of the company conspired with his receptionist against the authorities to conceal all evidence of his crime. I bet the captain of our team conspired with the coach against me and that's why I got traded.