Case File #5 begins with the boys and their father Fenton Hardy attending a party in New York City, thrown by Fenton’s former NYPD partner and current Chief of Police Samuel Peterson, who is announcing a mayoral campaign. Suddenly the lights go out, and when they are brought back on, Fenton Hardy is missing.
A mysterious videotape is sent to Sam Peterson. In it, a disguised voice claims to have kidnapped Fenton Hardy and infected him with a synthetic virus that is keeping him unconscious. The kidnapper claims that he is in possession of an even more lethal virus, which is all set to be released all over the city unless a huge ransom is paid.
The boys literally go underground, exploring the sewers and catacombs beneath the city to look for their father. They are assisted by Peter, a dispossessed homeless former lawyer who is a community advocate for other homeless sewer dwellers. But upon investigating further, the boys discover the horrifying truth - their dad’s kidnapper is an ex-convict former crime boss that Sam and Fenton put away. And now he’s out and thirsting for revenge.
Tropes found here are
- Deadly Doctor: Helmut von Reich, the inventor of the two viruses.
- Snake Oil Salesman: He was sent to prison for selling bogus cancer cures. And the viruses are complete fakes too. He’d just sedated Fenton Hardy earlier when pretending to inject him with one.
- Hostage Situation:
- Trask claims that the thugs the Hardys had captured earlier, whom Laura and Gertrude are holding captive at their home, have turned the tables and taken the women hostage, using this information as a deterrent to keep Fenton and the boys from defying him. It's revealed at the end that he was bluffing, and the Hardy women still have the situation under control.
- He then uses Fenton and the boys as hostages to get ransom money from Peterson, though luckily the Hardys manage to stop him and escape.
- King of the Homeless: Jones, who, after capturing the boys and discovering that they're on the same side, provides vital assistance in bringing Trask down.
- Made of Iron: Even with Frank, Joe, and Fenton all fighting Trask, he proves to be very difficult to take down, and almost smashes Frank's and Joe's heads together before Fenton finally manages to knock him out Just in Time.
- Revenge: Nick Trask wants revenge on Fenton Hardy and Sam Peterson for arresting him twenty years ago. In addition to murdering Fenton, he also plans to kill the Hardy Boys afterwards for some Revenge by Proxy.
