Roger Price is a retired NYPD officer battling depression after his wife and young daughter are killed by a drunk driver. He is contacted by a woman who claims that he is the father of her twenty-two year old daughter, Bonnie, who has leukemia and needs his bone marrow to survive. When Bonnie is diagnosed with leukemia, neither Claire, Brad, nor their other children are a match for Bonnie which stirs Claire's suspicion that Roger is actually her biological father. After learning about Bonnie and the possibility that he is her father, and that she is gravely ill, he vows to help her. Roger's bone marrow is a match, and DNA proves he is her father. Bonnie then undergoes dangerous "conditioning" with radiation prior to receiving Roger's tissue donation.
At the same time, Roger's best friend, Danny, also a retired NYPD detective, is pursued by gang members that he arrested while he was a rookie. They served their sentences and are seeking revenge. Danny moves in with Roger after his house is burned down by his pursuers. Roger is shot by a hit man when he foils an attempt on Danny's life. He is taken to the same hospital where his daughter is a patient awaiting his bone marrow. During recovery, he develops a delicate friendship with Bonnie as she tries to accept him as a father. After the lifesaving procedure, Claire shuts Roger out of his daughter's life because she is afraid that the men out to kill Danny - and now him - will murder Bonnie too, if they are together. Roger and Danny are chased and have a shootout with the remaining gunmen and are able to detain them for police. The gangsters are sent back to prison and both Danny and Roger assume they are safe.
While visiting the graves of his wife and daughter, Roger has an unexpected encounter with a recently paroled man who killed Roger's family. With his gun drawn, Roger resists the temptation to shoot him as punishment for the agony he's endured since his family was taken from him. He realizes that Bonnie's father, Brad, feels the same loss as he does since Bonnie was taken from him with the news that Roger was her biological father. He forgives the man and finally releases the pent-up anger he's carried with him since their deaths. Claire eventually allows Roger to see Bonnie and he is finally able form a bond with her and moves forward with his life.