Diana learns that the series of murders she's investigating is linked to a tragedy that occured in the Tunnel World more than 20 years ago.
Diana stalks a serial killer of ex-tunnel dwellers; Father reunites with a former love (Fionnula Flanagan).
Vincent destroys a drug lab in his rage over Rolley's heroin addiction and later discovers the lab belonged to Gabriel.
Father's visit convinces Joe to organize a citywide search for the house where Gabriel is holding Vincent captive.
Diana is seized by Gabriel's henchmen and forced to summon Vincent to the aid of his gravely ill son.
Diana brings Vincent to her apartment to recover from his injuries and, after hearing his story, offers to help him find his son.
Elliot Burch, framed for Moreno's murder, is visited by Gabriel who promises a restoration of Elliot's wealth and power if he betrays Vincent.
Gabriel hires an assassin to track down and murder Vincent; Diana discovers the entrance to the Tunnel World.
Vincent asks Elliot Burch to help him track down Catherine's killers and recover their child. Diana discovers the entrance into the Tunnel World.
Grieving Vincent retreats to a deep cavern; Joe begins an investigation into Catherine's murder; Detective Diana Bennett probes Catherine's death.
Catherine is abducted by the leader of a vast criminal empire and Vincent desperately searches for clues to her kidnapping.
Catherine and Father help Vincent recover his strength and memory, but his extrasensory bond to Catherine is severed.
Despite Father's advice, Catherine risks her life to follow a despondent Vincent into the underworld.
After Father discovers that Paracelsus posed as Elliott Burch, he agrees to reveal the horrifying truth about Vincent's birth and parentage.
A vindictive inside source contacts an investigative reporter in order to expose Vincent and Catherine's relationship.
Vincent witnesses a murder, but his inability to testify frees the two culprits, who vow revenge on Catherine.
Vincent persuades Catherine to help her former love (Edward Albert) who is the target of a lethal CIA investigation.
Catherine prosecutes a highly publicized case in which a respected businessman is accused of beating his son to death.
Catherine goes to Los Angeles to investigate a tape-counterfeiting case after a key witness is murdered.
A voyeur (David Neidorf) who has seen Vincent with Catherine terrorizes her with menacing phone calls.
The appearance of an artist who supposedly died two years earlier leads Catherine and Vincent to a baffling mystery.
Vincent reunites with his first love (Elyssa Davalos) as she tries to escape her tumultuous life above.
Vincent battles his desire for Catherine when she seeks comfort in the Tunnel World after her father's sudden death.
Infiltration of the tunnels by a band of violent outsiders brings out Vincent's uncontrollable dark side.
Catherine's loyalties are divided when she is assigned to prosecute a man who now lives as a respected member of the Tunnel World.
Vincent tries to help a disfigured outcast (Kevin Scannell) who is brought into the Tunnel World by Father's son (Bruce Abbott).
The secret of the Tunnel World is imperiled when a troubled boy (Jonathan Ward) follows Catherine into its depths.
Vincent's protege experiences ambivalent feelings when he returns to the world above and falls in love with Catherine.
In an attempt to live in the world above, a hearing-impaired woman from the Tunnel World joins a violent gang.
Catherine brings a pregnant ex-prostitute (Katy Boyer) to the tunnels, where the girl falls in love with Vincent.
Paracelsus returns for Winterfest with revenge on his mind; Father's life is threatened during the Tunnel World's annual Winterfest celebration.
Vincent helps a Russian sailor named Dmitri from drowning, unaware the man is a carrier of a lethal virus.
A frustrated Vincent is unable to help Catherine when she is endangered while investigating a case in Los Angeles.
Vincent and Catherine help a former piano prodigy named Rolley of the tunnel world, now a drug addict.
The 20th anniversary of her mother's death causes an emotional Catherine to question her relationship with Vincent.
Entrepreneur Elliot Burch's planned construction of a skyscraper threatens to expose and destroy the Tunnel World.
Father's evil former partner tries to rule the tunnel world by kidnaping Catherine and destroying Vincent.
Catherine puts her anger toward a Gypsy thief aside when she learns that he is the victim of an injustice.
The discovery of a lost pirate's treasure brings greed and jealousy to the Tunnel World, as well as danger to Catherine.
When Catherine learns that an old flame is terminally ill, Vincent fears that her love for him may be rekindled.
Catherine gets a new co-worker at the D.A.'s office and soon discovers that he has a connection to the Tunnel World.
Joe Maxwell's current romantic involvement puts a damper on the celebration marking the anniversary of Catherine and Vincent's first meeting.
Catherine and Vincent search for the dealer of a deadly hallucinogenic drug grown in the Tunnel World.
An arranged marriage and a tong war threaten the love of a Chinatown couple (Rosalind Chao, Dennis Dun).
Vincent and Father are trapped underground when they try to rescue a group of children playing in an unsafe section of the tunnels.
A hearing-impaired girl from the Tunnel World is the sole witness to the murder of a police officer, but her testimony could jeopardize her life.
Catherine investigates a respected children's home after information from Vincent indicates foul play.
Catherine becomes the target of a voodoo sorcerer as she investigates the bizarre murder of a wealthy businessman.
Vincent and Catherine search for Father, who has returned to the surface world for the first time in 30 years.
Vincent falls into the hands of an anthropologist who imprisons him for examination in a university lab.
A former "tunnel kid" (Asher Brauner) who is now a waterfront racketeer poses a threat to Catherine's life.
An Irish novelist's (Caitlin O'Heany) visit brings admiring Vincent to the street, but her enemies endanger Catherine.
Catherine's search for a witness leads her into a gang war; Vincent must come to her rescue.
Catherine falls in love with a powerful man; Vincent comes to the aid of elderly apartment residents being terrorized by thugs.
Catherine fears that Vincent might be the animalistic vigilante who is killing thugs on the New York subway system.
Catherine Chandler is attacked and left to die, but her life is saved by a mysterious man-beast who lives in a subterranean world.