The Fei Sisters took the instrument left behind by the earlier group of five and returned to where they had released the Mutant Rat. Unfortunately, the instrument could only detect where the Mutant Rat's signal had last disappeared; it could not retrieve the recording device tied to the rat.
"It should be somewhere around here." Xiao Fei pointed at the location on the map. "We checked this place before. It used to be an industrial area, and the pollution was quite serious. The sewers fermented year-round and turned into toxic gas. I saw very few Mutant Animals active here. That Mutant Rat may have wandered in by mistake and died inside."
The underground passages branched in every direction. Although they were filled with toxic gas, some pipes had ruptured and connected to the surface, so it was not completely devoid of daylight.
Xu Huo easily found the recording device he had placed underground earlier. However, it was no longer tied to the Mutant Rat and had instead been crushed into a pile of wreckage. It looked as though it had been flattened by pressure. Fortunately, the storage crystal inside had not been damaged and could be removed for viewing in another device.
However, after watching the entire recording, they learned nothing other than that the Mutant Rats entered deep into the Mutated Plants' territory through vine stems.
"Most of these Mutant Rats die in the vines, so why do they keep rushing in there in groups?" Xiao Fei could not understand it. "Didn't they say Mutant Animals become more perceptive after Evolution? Those Mutant Vines are poisonous."
"Perhaps it's biological instinct," Xu Huo said. Their collective migration might have originally been for survival.
"Then wouldn't that make it very hard to find?" Xiao Fei said regretfully. "I've never even seen