In Spidersilk the novel, the intruders are blind. However, they do have heightened senses in other degrees. For instance, in the novel, when Dacian approaches Chris while he’s working in his office he knows he’s there because his senses begin to tingle. This is actually a common occurrence in our own world when people lose a sense. Even in pop culture we can see some superheroes with heightened senses due to a loss of another! Take for instance, Daredevil who is also blind. Want to know more? Check out this link: http://www.sciencedaily.com/releases/2012/05/120508152002.htm