Still grieving over Darius' death, Duncan tries to elicit the meaning of the numbers Darius left him. He meets Joe and learns about the Watchers, who record the facts about Immortals but never interfere. Joe insists the Watchers would never have killed Darius. Duncan recognizes Horton as his attempted killer, and their conflict pulls Joe between them.

Duncan, Tessa, and Richie attend a photographic exhibit featuring Immortal Gregor, and Duncan discovers that the other exhibitor is someone he loved decades earlier, who had sent him away in order to focus on her work. She recognizes him, but he doesn't know how to tell her that he is the same man she loved. Meanwhile, Gregor appears to have changed since Duncan knew him, as he appears to have become disillusioned and can no longer feel emotion.

Duncan takes on Charlie DeSalvo to prove he's good enough at martial arts to work out at the dojo. Dawson tells Duncan that Quenten Barnes is free and killing mortals, but Duncan refuses to get involved. Then Duncan's old friend Michael Moore turns up, determined to take Barnes' head. In flashback, Michael was unable to save his mortal girlfriend Jeanette. Barnes beats Duncan to the priest who attended his execution, as Duncan tries frantically to prevent more killings.

Duncan proposes marriage to Tessa, but can he escape a long-ago curse as well as an Immortal who uses her as bait?

When Richie interferes with Immortal Annie Devlin and her IRA gang, she vows revenge. Meanwhile, Duncan starts teaching Richie. In flashback, Duncan rescues Annie from a massacre but refuses to help her crusade.

Charlie alerts Duncan to a mysterious man who may be able to reduce violence in "the Zone," a dangerous slum neighborhood.

Amanda shows up at the dojo with a suspicious offer of friendship. Then Duncan helps Amanda escape from two attackers that she insists she doesn't know. In flashback to 1930s Germany, Duncan is trying to help a scientist escape when Amanda attaches herself to him to get away from police chasing her. In modern day, Duncan tells Amanda about the Watchers but they discover the men chasing her are FBI.

Duncan allows the dojo to be used for a karate movie starring Jimmy, a former student of Charlie's. When one of the stunt men is poisoned, Duncan and Charlie think someone may be trying to kill Jimmy and suspect the Tong are involved.

Duncan saved Immortal Carl Robinson from lynching in 1926 Louisiana. Carl became a famous colored league baseball star with aspirations of becoming a politician, but he has since become disillusioned after seeing years of racism and corruption. He now lives on the streets and steals to get by. When he steals Charlie's car to get away from drug dealers after stealing their money, Duncan tries to help him overcome his longstanding hatred of and distrust for whites, and he helps him deal with a racist cop who is after him.

Immortal Anthony Galen attacks Duncan in a deserted amusement park. Losing, he tries to escape and hits mortal Tommy Bannon with his car, killing him. Duncan feels guilty over Tommy's death and tries to console his mother. In flashback, the fiancé of Duncan's current bed partner challenges him to a duel, but accidentally stabs the girl instead. Tommy's mother asks Duncan if Tommy's death was really an accident, telling him that Tommy was an investigative reporter and he had been scared of something. Duncan decides to find the connection between Tommy and Galen.

Duncan's old friend Tommy Sullivan wants Duncan to buy a piece of his fighter George, and help him win pretty Iris.

Richie rescues a young woman being chased by Immortal Mako. In flashback, Mako shows up to capture Tim, a friend of Duncan's. Is she innocent or is she using Richie?

While camping in the woods Duncan and Charlie help a frightened young woman and her baby flee from an abusive father-in-law.

Immortal Xavier St. Cloud has mortals shoot his Immortal opponents so he can take their heads. Joe tells Duncan about the killings to warn him, and soon St. Cloud and his henchmen show up at the dojo. Duncan discovers the supposedly-dead Horton is working with St. Cloud, and Joe knew that Horton was alive. Meanwhile, an army intelligence officer named Renee Delaney gets involved while she is investigating one of the men working with St. Cloud.

Renee and Duncan are attracted to each other but both are more interested in finding their quarry. Charlie recovers in the hospital from his gunshot wounds. Joe is torn between his loyalty to family and his friendship for Duncan. Nevertheless, he decides to tell Duncan where Horton and St. Cloud are hiding. Duncan confronts them, but they flee to Paris and Duncan and Renee follow them.

A friend of Duncan's is murdered in his pool. After his wake, Duncan notices an immortal named Nicholas Ward, who had once killed several people Duncan knew, arranging his victims to look like a vampire was responsible.

Security advisor Immortal Arthur Drake kills his President just before the signing of a peace treaty. Journalist Beth Vaughan is suspicious of Drake's claim that a sex partner did the murder. Duncan keeps Eli from shooting Drake at the ballet, and Eli tells Duncan how Drake killed his family. Between Eli and Beth, Duncan is drawn into taking Drake down.

Duncan interrupts the attempted theft of an Egyptian sarcophagus. Inside, he finds Nefertiri. As Duncan helps her adjust to modern life, they cross paths with Marcus Constantine, who she resents for his part in the Roman domination of Egypt.

Immortal Luther kills Immortal Rebecca by holding her husband hostage. Amanda, who was once taught by Rebecca, visits Duncan to grieve. They learn that Luther believes in a myth which states that the bearer of a magical crystal will be invincible. Realizing that Luther is trying to reassemble the crystal, which Rebecca had separated and given to her disciples, they try to stop him - but not necessarily together. In flashback to 850 AD, Rebecca rescues newly-Immortal Amanda from being burned with other plague victims and teaches her to be Immortal. In flashback to 1635, naive Duncan encounters his first fighting Immortal women, Rebecca and Amanda.

Someone is following Richie, killing mortals and making it look like Richie did it, so he goes to Duncan in Paris for help.

Horton, an old mortal enemy, puts a criminal through plastic surgery to make her look like Tessa.

False Tessa sets Duncan up for the final death.