This documentary reveals for the first time how highly-invasive spyware, which can capture the electronic communications of a town, can be purchased in a 'grey market’ where regulations are ignored or bypassed. Mass surveillance equipment can then be sold onto authoritarian governments, criminals or even terrorists. During a four-month undercover operation, an undercover operative filmed the negotiation of several illegal, multi-million dollar deals that breach international sanctions. The proposed deals include the supply of highly restricted surveillance equipment to Iran. An extraordinary agreement was also secured between them to purchase powerful spyware with a company who expresses no care for who was the end-user. Spy Merchants brings us into rare insights into the interactions between spies.