The team hunts a killer who seems to be targeting couples - dehydrating the husbands and smothering the wives - with a very unusual motive. Peter and Olivia try to come to terms with her surfacing memories and emotions from the original time-line and the fact that she's beginning to forget parts of her life from the new time-line. Meanwhile, Walter and Peter try to figure out September's disappearance from the lab the week before.
