What is the importance of pictures in the novel, Unbecoming?

Pictures are a way of saving a moment in time, and Katie uses them as a way of helping Mary remember things, making them symbols of Mary's lost memories and of Katie's desire to help Mary avoid the fears that accompany her memory loss. Some pictures have specific purposes and symbolism. For example, the photo Pat sent Mary of Caroline as an infant was a symbol of the secure life that Pat and Lionel were able to provide, and that prompted Mary to end her efforts to get Caroline back