Widow Tong Suk Fan has raised her two sons, Yau Ching and Yau Kit, through years of hardship. Now grown, both brothers proudly serve in the Anti-Terrorist Force — one in Intelligence, the other in Operations — earning the respect of their boss and bringing pride to their mother.

But when a secret investigation puts them on opposite sides, their strong bond begins to unravel. Yau Ching, tipped off by journalist Yip Ting, uncovers a hidden threat and is nearly killed while digging deeper. Forced into hiding, he secretly continues his search with help from his girlfriend, intelligence analyst Yat Ka, and discovers a mole may be hiding within the agency.

As Yau Kit starts to suspect his brother and grows closer to Yat Ka, Yau Ching finds unexpected support — and love — in Yip Ting. With the truth buried under layers of deception, Yau Ching must decide how far he's willing to go, even if it costs him everything.