Han Seo-a, codenamed "Ironhand," is an elite bomb disposal operative who leaves the military to become a stay-at-home mother and support her husband, Min Tae-hwan. On their seventh wedding anniversary, she travels with her son to reunite with her husband, only for terrorists to attack their hotel. Amid the chaos, Seo-a discovers Tae-hwan's betrayal, and is devastated when her son abandons her over his father's mistress.
