Annie is plagued with curiosity about what goes on during Eric's therapy, but panics when his doctor invites her to attend one of their sessions. Meanwhile, Lucy tries everything to get excused from jury duty, upsetting Kevin in the process when her views of the judicial system are different from his own. Also, Chandler confesses the extent of his feelings for Roxanne after she is stabbed on the job by a homeless man. Lastly, Ruthie fears that her parents may be heading for divorce court after overhearing them fight.
Boston is at the mercy of a blizzard and the morgue staff at the mercy of an unknown toxin. With bodies piling up, and the lights out, the race is on stop this invisible killer before too many more die.
Although conflicted by his feelings for Amy, Ephram finds himself serving as confidante and friend to Amy's boyfriend, Colin, who continues to feel like a fish-out-of-water as he attempts to reclaim his life before the accident. Meanwhile, Andy hopes to convince Ephram to resume the piano lessons he abandoned after his mother's death; Nina's absentee husband (guest star Dylan Walsh) comes home for a visit, which proves to be far from happily ever after; and in a bittersweet turn of events, Amy and Colin are nominated for Homecoming King and Queen.
Horatio investigates the death of a man who accidentally inhaled a lethal combination of chemicals in a neighboring house after he went inside to retrieve his cat. Elsewhere, a resident of a retirement community is found dead in a pool of blood, an apparent victim of a vicious attack.
On the day of Owen and Chrissies wedding, Chrissie asmits her true feelings to Ed and Owens daughter is aginst the wedding. At the hospital, Kath gets worried when the police ask her questions about Terry's death and they decide that they need to exhume his body.
