Huang Donglai's strategy essentially consisted of three steps.
The first step — he and Linghu Xiang would leave the room on the pretext of needing to defecate and head to the latrine.
Why two people instead of four?
It was quite simple; if four people suddenly burst out claiming they needed to defecate, it would look suspiciously like a ruse and they might not be allowed to go.
Moreover, if they were allowed and all four went, wouldn't the guards assigned to them have to follow too?
So, in the current situation where both sides hadn't yet come to blows, going in pairs or alone was a wiser choice. Even if the officials were suspicious, they could only afford to send a few men, granting Huang Donglai and Linghu Xiang some room to create mischief.
The second step — Set off an explosion in the latrine, causing chaos.
