Along Came a Spider is the first of the Alex Cross books by James Patterson.
The story begins with the main character, Alex Cross, investigating three murders in a poor district of Washington DC. (The murders appear to be linked to another murder that happened earlier in DC.) Cross becomes angry when he is ordered to leave the investigation of a prostitute and her two children to investigate a pair of kidnappings: the daughter of a famous actress and the son of the Secretary of Treasury. Cross follows the ransom to Florida, but the boy is found dead. At this point Cross becomes the "delivery man" for the ransom.
He follows the instructions but ends up in a plane with the man demanding the ransom. In South Carolina, when they land, there is a fight between the two. During the fight an unseen second kidnapper disappears with the money. When the police look over the property, they find the two empty graves where the children were being hidden. Cross becomes the scapegoat for the failed rescue of the little girl (Maggie Rose). He is removed from the case, but decides to continue investigating.
During his personal investigation he ties the deaths of the prostitute and her children to the case of the kidnapped children when he investigates the murder of a teacher at a private school. Through the ensuing investigation they find out that a man by the name of Murphy was selling heaters door to door. Cross follows the lead but the kidnapper manages to escape. A couple of days later, Murphy takes the customers at a McDonald's restaurant hostage. This leads to Cross arresting Murphy/ Soneji. When Cross interrogates Murphy/Soneji he doesn't seem to be the type of guy to carry out the crimes that they have been investigating. Most of the people involved in the investigation begin to suspect Murphy/Soneji has multiple personalities. Cross does not. During the trial, the multiple personality theory culminates in Cross being asked to hypnotize Murphy/Soneji. It is a failure and the jury finds Murphy/Soneji guilty.
Cross does not give up on the girl. He becomes suspicious once he learns that the secret service are investigating the Secret Service agents that were at the school during the kidnapping. (This includes Jezzie, who Cross had an affair with during the initial investigation.) Soneji (the sociopathic side of Murphy) escapes from prison and tortures one of the FBI Agents Devine. It turns out that Devine and his partner Chakely took the ransom money, hired the pilot, and then killed him. After getting his money, Soneji kills Devine and escapes.
Cross invites Jezzie on a romantic trip. Jezzie admits that the ransom was her idea. Cross' old partner records the confession and Jezzie is arrested. It is revealed that Maggie Rose (the kidnapped girl) is in South America.
Case over, Cross returns home only to be attacked by Soneji. Cross protects his family and Soneji goes on the run through Washington DC. He ends up taking two children hostage. Cross and his partner eventually capture Soneji and he is put in a mental institution. Jezzie and the remaining partner, Chakely, are convicted of murder and kidnapping. They are executed. The end of the book shows that Soneji isn't done with Cross when he writes a letter and has a guard put it on Cross' windshield.