Robert McCall is a former agent of a secret government agency who is now running his own private crime fighting operation where he fashions himself as "The Equalizer." It is a service for victims of the system who have exhausted all possible means of seeking justice and have nowhere to go. McCall promises to even out the odds for them.

Financial wizard "Doc" Fletcher is sent by crime boss Joe Fiore to buy a bank in Switzerland in order to more easily launder their profits. When he arrives, Fletcher finds that the bank, acquired by his associate Prince di Siracusa, consists of some shabby offices above a restaurant. To make up for this, the Prince suggests that Fletcher invests in a silver mine owned by Shireen and Agha Firdausi. This solves one problem, but the mine also attracts the attention of some of the most powerful people in the silver business. Fletcher must pull out all his wheeler-dealing skills in order to keep hold of everything he's worked for, in the process romancing a banker's discontented wife.

Thomas Jerome Newton is an alien who has come to Earth in search of water to save his home planet. Aided by lawyer Oliver Farnsworth, Thomas uses his knowledge of advanced technology to create profitable inventions. While developing a method to transport water, Thomas meets Mary-Lou, a quiet hotel clerk, and begins to fall in love with her. Just as he is ready to leave Earth, Thomas is intercepted by the U.S. government, and his entire plan is threatened.