When Catherine Chandler is abducted, beaten, and slashed by some men who mistook her for Carol Stabler, she is saved by Vincent (visibly human but has the appearance of a lion) who takes her to "The World Below" to recuperate, and the two form a strong friendship.
The very next day when investigating an illegal escort service run by Martin Belmont, her life ends up in danger until Vincent comes to her rescue.
The other man, graduate student Jonathan Gould, believes Vincent is a freak of nature, and wants to reveal him to the public and become famous.
Catherine and Vincent must dive into Father's past—where they learn of his true identity, Jacob Wells, a physician; his blacklisting during the McCarthy era; and, of his long-lost wife—to clear his name and reunite him with his now-dying wife.
Catherine learns that a city's model, Ridley Foster Home, holds a dark secret: selling orphaned children to criminals who force them to steal.
Upon witnessing a shooting, deaf Laura Williams (Terrylene) must decide if she should leave the sanctuary of "The World Below" to free an innocent man.
The inhabitants of "The World Below" shun Mouse for his acts of thievery, until they need him and his mechanical and engineering intelligence to help rescue Father and Vincent following a cave-in.
Mouse, in turn, needs Catherine's help...which sends her reluctantly to Elliot Burch for specialized construction equipment that may free Father and Vincent in time.
Chinatown is the setting of a "Romeo and Juliet"-like story of a woman who is friends with Vincent and who has fallen in love with one man, but—through an arranged marriage—has become engaged to the son of a Triad leader.
Meanwhile, Vincent travels to a deep chamber to find a gift for Catherine, in celebration of the one-year anniversary of their first meeting.
Vincent has foreboding dreams when Catherine's former fiancé Steven Bass returns to her life, and with good reason: Catherine is barely aware Steven—whose parents are now dead and who's dying of brain disease, but whose becalmed manner at first belies that he's still a control freak—is obsessed with making her the wife she doesn't want to be to him, and goes to troubling extremes to make it happen.
Through a series of flashbacks, we learn Rollie feels responsible for the death of a helper who taught him to read music.
Little does anyone know, Dimitri is carrying the pneumonic plague which soon becomes an epidemic amongst the residents of the tunnels and begins taking lives.
Laura's boyfriend in the gang, Jerry, is an undercover police officer who reveals his secret to her, prompting her to run away.
Catherine discovers his warrant by accident and doesn't want to force Kanin to leave his family, but Vincent convinces him to face his responsibility and give closure to the still-grieving woman.
One night she is visited by her father's spirit in a dream and she comes to terms with losing him, which gives her the strength to return to her world.
Guest stars: Fredric Arnold as Jay Coolidge, Douglas Roberts as Mark Coolidge, Kate Williamson as Marilyn Campbell, Abraham Alvarez as Dr. Cherian, Carolyn Finney as Rita Escobar, Dion Basco as Paco Former "World Below" resident Lisa Campbell – now a world-famous ballerina — returns to the tunnels for refuge, desperate not to testify against her controlling and arms-running boyfriend.
Her return unnerves Vincent—who loved her when they were teenagers, but who injured her once during an embrace, a major reason he fears physical intimacy with Catherine.
An eccentric young artist calling himself Kristopher keeps appearing in Catherine's life after meeting her in a bookstore—including near a tunnel entrance where he sees Vincent.
Catherine and Joe have been working on a case involving a high-power Wall Street celebrity whose child abuse resulted in the death of his son.
Following the death of Paracelsus, and Father's revelation of the truth about his abandonment and adoption, Vincent comes to terms that the beast within him is causing him to lose control until Catherine daringly joins him to comfort him through it.
When an explosion lands Joe in the hospital, Catherine learns that she is pregnant and ends up captured by a crime syndicate led by a shadowy figure during her investigation.
Meanwhile, Joe has become acting district attorney in the wake of Moreno's exposure and murder and is free to continue his own investigation.
Following the boat explosion, Diana finds a wounded Vincent at Catherine's grave and takes him back to her apartment to heal.
Diana removes all news items and written evidence involving Vincent's rescues of Catherine in danger from her working wall board.
Diana investigates the strange murders of ex-inhabitants turned helpers of "The World Below"—all of whose faces are covered in blue ash.
He returns to the tunnels and discovers former inhabitant Gregory Coyle has committed the murders—seeking revenge for the death of his father by cave-in 20 years ago.
Gregory buries Father alive in a little-used tunnel but lets himself fall to his own death despite Diana and Vincent's rescue attempt.