I have translated the text you provided line by line as requested:
Wan Yan Jun had a good plan, yet things did not develop in the direction he had hoped.
Since Grant Valley Master Thomas had set a trap to lure them here, how could he not have a thorough strategy?
If the only objective was to trap them, wouldn't the trap be a bit too rudimentary?
"Pfft!"
Just as Wan Yan Jun, prepared to put everything on the line, suddenly spat out a mouthful of green blood.
"No good! We've been infected by the plague!"
Only then did Wan Yan Jun suddenly realize where Grant Valley Master Thomas's confidence came from.
The entire Plague Valley was most contaminated with plague right here at the estate, and the color of the fog had turned blood red.
Unfortunately, the three of them saw Ling Xiao unaffected and assumed that the dense fog was merely imposing in appearance and, in reality, harmlessly brashly entered.
However, only now did they suddenly understand the gravity of the situation.
