Derek has been sent an urn with the ashes of his former lover Laura. He is about to scatter her ashes, and Rachel offers to help him. He refuses, but says that he is surprised that it is so hard even though it has been such a long time since he last saw Laura. He tells her that it's been twenty years since he saw her and that he always assumed that they would meet again. Derek also says that out of the blue a lawyer sent him the urn with her remains along with a small rock - half of a fossil leaf. It's the last thing that she ever gave him to remind him of her.
Outside by the water, Derek scatters Laura's ashes in the wind. A young, dark-haired man is watching him. When Derek looks back, the boy is gone. Back inside the castle, Rachel introduces him to Lucas, who claims to be his and Laura's son. Lucas says that the attorney told him how to get in touch with Derek, and he gives Derek the other half of the fossil leaf as proof that he is Laura's son.
Nick, Alex, and Rachel are discussing Lucas. Nick is unconvinced that Lucas is really Derek's son, and thinks that Derek should request a blood test. Rachel explains how upset Derek was by Laura's death, and suggests that they withhold judgement on Lucas. Lucas walks in and hears Nick's statement about needing to see his birth certificate. He asks if it's okay if he takes a look around, and leaves the room, after exchanging an odd look with Nick.
Derek is on the phone with the hospital where Laura gave birth. They tell him that he is listed on the birth certificate as the father and he asks for a copy (for you detail gatherers, his fax number is 415-555-0130). In Derek's room, Lucas is looking around. We see a very demonic expression cross his face, and he stretches out on Derek's bed and lounges around looking really, really creepy.
Rachel meets Derek in his office where he tells her about the birth certificate. Rachel is really excited for Derek. He is excited and guilty at the same time. He feels like he needs to make up to Lucas for the past 20 years of not being there. He tells her that he's afraid of being too much like his own father, and that he's worried about explaining the Legacy to him. Rachel convinces Derek that he will do fine.
In the yard, Nick is working out - practicing his karate. Lucas is watching and makes a sarcastic comment that he is better, and that Nick should be 'tested' by him. Nick responds calmly that the first rule is silence. Lucas challenges him again, but Nick refuses. Lucas accuses him of being afraid of losing and makes a move on him. Nick defends himself, giving Lucas a bloody lip, and Derek interrupts them before they can fight any more. Lucas uses Nick's towel to wipe the blood off his mouth and leaves with Derek.
That night in Derek's office, Lucas finds Derek studying Winston's journal. He asks to read it, but Derek refuses and locks it in his desk. Derek struggles to find some common ground with Lucas and offers for them to do something together. They decide to go white-water rafting because that is something that his mother enjoyed. They decide to go the next day. After Derek leaves the room, Lucas manages to unlock his desk and get Winston's journal. As he reads it, we see that demonic expression again.
The next day, Lucas and Derek are leaving for their trip. Rachel offers to help, and Lucas treats her rudely. Derek tells her that he isn't taking his cell phone, and says that if they need him that Nick can get him with the chopper. Alex is to pick them up the next evening. Nick and Alex say privately how they are still suspicious about Lucas.
Before going rafting, Derek takes Lucas to meet his sister the nun at her convent. She is thrilled to see Derek, but is a little hesitant about meeting Lucas. She tells Derek that Lucas looks much like he did as a young man. Lucas behaves rudely and angrily toward Ingrid, but she hugs him anyway. Lucas goes to the car, and Derek apologizes for his behavior. She tells him that she is worried for his safety and warns him to be careful.
Back at the castle, Nick tells Alex and Rachel about using the blood from the towel to determine if Lucas is Derek's son. He goes on to tell them that a background check on Lucas turned up absolutely nothing. Rachel suggests that they go see the lawyer that sent Laura's ashes to Derek. But, at the lawyer's office, Nick and Rachel find out that they lawyer that supposedly sent Laura's remains to Derek is dead -- he committed suicide three weeks previously.
At the river, Derek and Lucas meet up with Justin the river guide. Justin is uncertain about the weather, but takes them anyway. Justin and Derek are old friends and are reminiscing about old times on the river (is there anything Derek hasn't already done?) The scenery from these scenes on the river is really beautiful.
Further down the river, Derek has them stop where he and Laura last went camping. He shows Lucas the spot where Laura found the fossil. Lucas asks him if he loved Laura, and Derek says that he did, and he asks Derek about his 'world'. Derek tells Lucas that, like him, he grew up without knowing what his father did, and that he was fifteen before Winston tried to show him. He tells Lucas how Winston was killed in Peru, and that he swore he wouldn't follow in his footsteps. But, back at school, he found out that he was a lot like Winston - driven and obsessed. He fell into teaching, and he ended back at the Luna Foundation. He tells Lucas that he finally found something worth dying for and that the Luna Foundation (i.e. the Legacy) is his passion.
Justin suggests that they camp there and that they run the rapids the next morning. Lucas wants to continue, and complains about Justin being there with them. Derek realizes that Lucas sounds just like he did the last time he and his father argued.
Back at the castle, Nick and Rachel realize that the letter from the lawyer was dated after the lawyer's suicide. They get the doctor's name from the birth certificate (which was faxed from the hospital) and decide to see the doctor.
At the camp, Lucas asks Derek about the Legacy while Justin is down at the river. He tells Derek that Laura mentioned the Legacy right before she died, and that she told him that Derek would explain everything. Derek hesitates to say anything, but tells Lucas that forces of evil overwhelmed Laura and that she tried to kill him. Because she loved him, she ran away trying to escape the evil. Derek tried to find her and bring her back, but was unsuccessful. Lucas accuses him of lying to him, and stalks off toward the river. Justin tries to make small talk, and tells Lucas that he knew his mother and that he helped her to find a doctor to deliver him when he was born, and that he promised never to tell anyone. Lucas attacks Justin and kills him, dragging his body into the river.
Nick and Rachel have gone to see Laura's doctor. Dr. Risling is now in an insane asylum. He is in a straight jacket and thinks that Rachel is there to examine him. They ask him questions about Laura and he is immediately afraid. He says that "he" has been speaking to him, and denies any responsibility for what happened. He says that she and the baby died 20 years ago -- with blood everywhere. He says that "he" told him to bury them by the peach orchard and not say anything, and that nobody would ever find out. He starts thrashing around the room and foaming at the mouth and Rachel and Nick have to leave.
The next morning at the campsite, Derek (looking wonderfully scruffy) realizes that Justin didn't sleep in his tent during the night. Lucas (sporting major attitude) says that he hasn't seen Justin. Derek goes to check out the river and tells Lucas to break camp.
Back at the castle, Nick and Rachel realize that Derek must be in trouble. Alex has already left to go meet them at their appointed meeting place. The get the results for the DNA test which shows that Lucas's blood has inhuman qualities.
At the river, Derek spots Justin's body caught in some debris. Lucas tries to keep him from going, but Derek insists on going after Justin's body. While trying to get to the body, Derek and Lucas fall out of the raft and are swept down stream. Alex, who is waiting for them on the bridge, is contacted by Rachel and Nick that they are heading out in the chopper to find Derek.
Derek has washed ashore and is looking for Lucas along the river. He eventually finds him unconscious, and struggles to awaken him. Meanwhile, Rachel and Nick (flying along the river in the chopper) are concerned that they won't find them before dark.
Derek has lit a fire, and Lucas confronts him. Derek says that he knew that Lucas was lying when he said that his mother told him to ask Derek about the Legacy. He tells Derek that the real Lucas died a long time ago, and that he did not kill him. He says that he wants to become Derek Rayne - take his body and use it to destroy the Legacy from within. They begin to struggle and Lucas does some really fancy face morphing into Derek and other demonic faces. They end up in the river, where Derek begins to choke the demon-Lucas, but he makes himself look like Ingrid to try and stop him. Derek refuses to listen and drowns the demon, which disappears. Beneath the water he sees a vague shape of something indescribably evil.
Nick and Rachel find Derek sitting sadly by the fire waiting for them, and they wrap him up in a blanket and take him home.
Derek's entry in his journal reads: