Tennis player turned coach Tashi has taken her husband, Art, and transformed him into a world-famous Major champion. To jolt him out of his recent losing streak, she signs him up for a "Challenger" event — close to the lowest level of pro tournament — where he finds himself standing across the net from his former best friend and Tashi's former boyfriend.

Robert McCall, who serves an unflinching justice for the exploited and oppressed, embarks on a relentless, globe-trotting quest for vengeance when his former partner is murdered.