plot with somebody
collude - plot
When you ‘collude’, you co-operate with somebody secretly, especially to do something dishonest or illegal. This formal word is typically used in reference to something high-level, such as a scheme or plot hatched between governments, powerful figures, or large companies, but it is not necessarily limited to that.
The two most prominent companies in the industry stringently deny claims that they agreed to collude to keep oil prices artificially high.
The official investigation could uncover no evidence of collusion between the newly elected government and the foreign country accused of meddling in the election.
Senior figures at the firm colluded to keep the extent of the crisis secret from the public so that they could sell their shares before the stock tanked.