Fog-bound Yangtze night. The gunboat sits almost swallowed by grey-black river air while a dark junk waits offshore.

Tang receives and studies the order that brought him to the bow.

Inside the radio cabin, Wei joins Lin for the locked watch and the door is secured from outside.

Lin notices evidence that an order in her name has been used, while Wei pretends it is routine paperwork.

Tang remains exposed at the bow while the junk adjusts position in the fog.

The timing signal begins. Lin hears the operation confirm itself.

Lin tries a practical excuse to leave, but Wei closes it down.

Lin considers an unsigned alert, and Wei reminds her exactly how it can destroy her.

The timing window shrinks as the trap advances.

Lin remembers Grandmother Luo teaching the clear-signal version of the grandmother-cipher.

Lin chooses the grandmother-cipher and prepares to broadcast in the clear.

Lin begins the clear-signal Wu grandmother-cipher under the cover of fish prices.

The coast-watcher net hears the open grandmother-cipher and understands the warning.

The kidnap junk receives the warning and abandons the approach despite Tang being exposed.

Wei realizes Lin has used a live hidden channel, and Lin presses through to complete the warning.

Lin imagines what exposing the grandmother-cipher may bring down on her village.

The junk turns away, and Tang realizes the radio cabin is the source of the strange warning.

Wei tries to subdue Lin before anyone can open the cabin.

Tang reaches the radio corridor and forces the crew to give him the outside key.

Lin fights to reach the door as Tang unlocks it from outside.

Tang enters with revolver drawn and stops Wei before he can continue the attack.

Tang confirms the forged order and Wei tries to turn suspicion back onto Lin.

Tang asks what Lin sent, and Lin cannot yet tell him the full price.