At an Easter day picnic in a picture-perfect town, little Michelle Crittendon is startled by a raven in the woods. Her mother, Martha Crittendon, isn't happy when her husband won't cut short his business trip to tend his distraught daughter. Forced to stay home alone that night, Martha's worry turns to fear at the sight of the raven on her mantle. Suddenly, a mirror shatters and a large, monstrous creature appears from nowhere and attacks Martha.

Mulder is called away from a strip club stakeout, leaving Scully to handle the surveillance alone. Skinner wants Mulder to investigate Martha Crittendon's disappearance since the presence of ravens suggests an oddness about the case. The fact that Martha's father is a federal judge certainly makes the case a priority.

Sheriff Phil Adderly fills Mulder in at the crime scene. There is no ransom note, prints or blood evidence, but there are four deep scratches on the mantle in the otherwise pristine house. Mulder wonders if raven talons could have made the marks and carefully notes the broken mirror. Howard Crittendon, Martha's husband, shows Mulder birth control pills in Martha's name. Since he has had a vasectomy, Howard thinks Martha has run off with a lover, and he produces an unknown key he found among Martha's things.

Ellen Adderly, the Sheriff's wife and a close friend of Martha's, posts flyers regarding Martha's disappearance. A tough-looking woman named Jenny approaches her as Martha spots a raven nearby. Although they have a mutual dislike, Jenny tells Ellen that they have more in common than she knows. Ellen turns away from Jenny to see a monstrous reflection in a car window. The window shatters instantly.

Scully phones Mulder from the stakeout. She's cold, hungry and not finding anything of substance on her surveillance. Mulder has no time to sympathize with her plight as he digs in to Ellen Adderly's home cooked meal. Ellen invites him to stay at her home while he works on the case.

Young Michelle Crittendon sees the raven again outside her house, and her father Howard follows the bird into the garden to find a siege of ravens pecking at the flesh of a human hand. It is Martha's body, buried in her own backyard. Later, the coroner tells Mulder the gashes on her body resemble a bear attack, although bears don't generally bury their prey. Sheriff Adderly and Mulder both agree that Howard Crittendon murdered his wife. Ellen arrives at the crime scene, devastated. She admits that she may have seen the creature earlier that day.

As the Sheriff calms his wife at their house, Mulder theorizes that reflective surfaces act as doorways to the spirit world. An evil entity might be summoned through that portal, taking the form of a raven. Mulder is lead to Jenny as a possible enemy to Martha, but she denies any connection to the murder. Mulder doesn't question her innocence, but is suspicious when she says that she was alone all night.

Ellen is puzzled to find a key in her carpet that matches the one Howard Crittendon gave to Mulder. Suddenly, a noise emanates from her baby's room and distracts her. She runs in to see a raven sitting on the edge of the crib. Ellen shoos it away, but then sees a reflection of the creature in a mirror, which shatters. Terrified, she grabs the baby and hides in a closet. After her husband rescues her, she tells Mulder that the creature had chased her. The sheriff takes Mulder aside and asks him not to encourage his wife in what he feels are her stress-induced delusions. Mulder spots the key on the floor and asks Ellen about it. She says she found it right before the raven attacked her.

Late that night, the sheriff rises from his and Ellen's bed and dresses to leave. He goes to a motel and unlocks a room with the key his wife uncovered. Inside is Jenny, awaiting her lover. Although Sheriff Adderly protests that they need to discontinue their affair, Jenny lures him into bed.

The next morning, Mulder is up early and finds that Ellen has laundered his shirt and prepared a huge breakfast for him. She senses that he likes to be taken care of, and asks why he has no one in his life. The sheriff returns home, interrupting their conversation. He makes up an excuse that he had to cover for another deputy. Mulder lets him know that the medical examiner found that Martha had been four weeks pregnant when she died, in spite of taking birth control pills. Since her husband had a vasectomy, Mulder questions whom the sheriff may suspect. When Adderly has no answer, Mulder calmly asks for the motel key.

Jenny hears ravens cawing outside the motel room and she dresses. The mirror above the bed suddenly shatters, and Jenny is attacked. She manages to slash at the creature's shoulder with a bit of broken glass before it kills her. At this newest crime scene, Mulder discovers the key fits the lock to the motel room. He confronts the sheriff about an affair with both Martha and Jenny. Now a suspect, Adderly is finally ready to listen to Mulder's theories about the ravens.

Ellen gets ready to take a bath and discovers a bloody gash on the back of her shoulder. Distressed, she flashes back to her struggles with Jenny. Mulder heads back to the Adderly house, but takes a phone call from Scully about wrapping up her stakeout. The perpetrator they were looking for had been right under their noses, dressed like a woman. Mulder makes a connection to the Crittendon monster and rushes to the house. He tries coaxing Ellen from the bathroom, telling her that he knows what she's done. She tells him that her whole marriage was a lie, and she wished Mulder had never come there. Suddenly, the creature bursts through the door and attacks Mulder, pushing him under the bathtub's water. As he struggles for air, the creature sees its reflection in the water and stumbles back, releasing Mulder. Ellen, having transformed from the creature back to her normal self, is curled up in the corner of the bathroom weeping.

Mulder visits Ellen later at a psychiatric facility. The sheriff says that his wife has a dissociative disorder, or split personality, but that he doesn't understand how it that is responsible for the turn of events. Mulder thinks that Ellen found a way to rationalize her husbands' affairs to protect her family. He suggests that this may be as close as science can get to an explanation for what happened. In her cell, Ellen stares at a raven outside her window.