Jeremiah Ecks (ANTONIO BANDERAS) is a former covert FBI agent who's lured back into duty by Julio Martin (MIGUEL SANDOVAL). Martin has information about Ecks' wife, Vinn, who was believed to have been killed in a car explosion seven years ago, but won't tell the sullen agent any details until Ecks agrees to investigate Robert Gant (GREGG HENRY).
It seems that the shady character has acquired a microscopic killing device that, when injected into its victim, can kill them and make the assassination look like a normal heart attack. Worried that Gant's attempting to get the device into the country or has already managed to do so, Julio teams Ecks with Harry Lee (TERRY CHEN) and the two attempt to find him. Ecks' desire to do so grows when he learns that Gant knows about his wife.
Their task is a bit easier since Gant and his right-hand man, A.J. Ross (RAY PARK) are out trying to find Gant's kidnapped son, Michael (AIDAN DRUMMOND), as well as his abductor, another former covert operative known by the name of Sever (LUCY LIU).
She has a serious bone to pick with Gant and will only exchange Michael for Gant's life. A proficient and highly trained killer, Sever has the upper hand in the situation and quickly proves her formidableness in easily dispatching Gant's men. Complicating matters is Gant's estranged wife, Rayne (TALISA SOTO),
who isn't happy with her husband and is naturally worried about Michael.
As the two covert operatives attempt to find and stop Gant, their paths repeatedly cross and antagonistic sparks fly between them. Yet, they eventually realize they have a common goal and thus set out to work together to fulfill their respective missions.