The specific hiding location of Maria Edwards is on the South Shore of Green Lake, just as the witches once mentioned to Shard. The soul that fled from the island entered an area of long-existing spatial anomaly, thus avoiding detection for many years.
The characteristic of that spatial anomaly area is a "Hidden Space," which overlaps another unobservable space over a normal space, only accessible through special means.
This sounds quite similar to Green Lake's Central Island and "another island," though the latter involves the entire material world's spatial balance, and is fundamentally different.
Miss Sylvia's followers discovered that region, and after repeated confirmation, found that even Miss Sylvia herself could not enter the hidden space. Therefore, she contacted Shard through Miss Galina, asking Shard to bring Laster Edwards along.
After all, Laster Edwards is also a spirit, possibly able to find a way to enter.
