plot against (something or someone)
To join together to form a scheme or plot to foil or defeat someone or something. The group was arrested for plotting against the monarch. His two younger brothers plotted against him to have him removed from the head of the company.
plot against someone or something
to make a scheme against someone or something. All the counselors plotted against the czar. We plotted against the opposing party.
plot against
v. To establish a plan to overthrow or ruin someone or something: The spies plotted against the government.