As Marty Glenn, a twenty-something woman, moves about her apartment, she suddenly experiences an internal vision. As she watches, horrorstruck, a murderer, switchblade in hand, advances on a another man standing before a bathroom sink. A short time later, police are summoned to a motel, where the body of the murderer's victim lies on the bathroom floor. Marty, a bloody sponge clutched in her hand, is discovered hiding in the shower. As the officers place Marty into handcuffs, they realize she is blind.

     Scully and Mulder meet with Wilmington Homicide Detective Lloyd Pennock, who has been assigned the murder case. Pennock explains that, under normal circumstances, Marty would have been charged with the murder. But since Marty has been blind since birth, he is at a loss as to how--or why--she managed to kill the heroin dealer, Paco Ordonez. Pennock states that he has 48 hours to prove to the District Attorney that his suspect possesses a kind of "sixth sense"... or wait until she kills someone else.

     The detectives meet with Marty inside her jail cell. During questioning, it becomes obvious that Marty--who has adopted an uncooperative attitude--possesses knowledge that only the murderer should know. As Mulder stays behind to supervise Marty's polygraph test, Scully visits the scene of the crime. There she discovers a bloody leather glove hidden behind the bathroom mirror. Meanwhile, by phrasing a question in a certain manner, Mulder determines that Marty did somehow manage to witness the murder.

     Marty experiences another internal vision. This time, the killer makes advances on a sexy woman, Susan Forester, who sits at a bar. Marty notices the name of the bar reflected in a mirror. She requests that she be allowed to make a phone call from jail. By using an information operator, Marty phones the bar and makes contact with the murderer, a man named Gotts. She warns him to leave the woman alone.

     Scully brings the bloody glove to the jail. She informs Marty that her fingerprints were located on the glove, and perhaps even more importantly, the glove fits Marty perfectly. Pennock concludes that Marty is the murderer. Mulder, however, is plagued with doubt. Scully offers a possible explanation: Marty may not be blind. Scully expands upon this theory, noting disorders that would permit sight on a subconscious level. As Marty undergoes an eye exam, she is suddenly struck by another internal vision. Mulder notes a reaction on a measurement mode screen used by the opthamologist. But Marty refuses to explain what she saw. Though the examiner concludes that Marty is completely blind, Mulder tells Pennock and the District Attorney that there is evidence of neurological activity which caused her pupils to dilate--perhaps a physical response to images in the mind's eye. The District Attorney concludes that it is unlikely her office could convict a blind woman based on fingerprints alone. As a result, Marty is released from custody.

     As Marty makes her way through the city, she is struck by another vision. This time, she witnesses Gotts attack the sexy woman from the bar. With some help from a passerby, Marty makes her way to the alley where the attack occurred. She discovers the woman's body inside a dumpster. Marty then returns to the police station and confesses to both murders.

     Marty supplies Pennock with the location of a locker that contains a briefcase filled with Gotts' heroin. Meanwhile, a lab test reveals that neither of the stains found on the leather glove match Marty's blood type, bolstering Mulder's suspicion that Marty is innocent. So confident is Mulder that he approaches Marty directly. He tells her he discovered the original police report detailing her mother's murder--a single stab wound to the right kidney--which is identical to the manner in which Ordonez and Forester were killed. Mulder concludes that Marty gained her unique sense when her then-pregnant mother died at the murderer's hands.