After leaving Wan Shouguang, Yan Junze didn't walk far, but wandered around the area before returning to the vicinity of the villa.
He had been pondering, "Resurrection" was the hint provided by the mission information, and the way Wan Shouguang and his wife were acting so secretively, it felt like they were hiding something.
If their son had been resurrected, and the couple was hiding something, it could be that Wan Cong's resurrection involved some unconventional methods.
However, the mission details were very clear, stating that this strangeness wasn't newly born, but had existed for some time and had made contact with other strangenesses.
Looking at it another way, if the couple's son was resurrected, it was likely that he was being possessed by another strangeness rather than actually being brought back to life.
With this question in mind, Yan Junze returned to the grave where Wan Cong was buried and carefully examined the soil that had been used to cover the grave.