- For the episode of Wolfenstein 3D titled "A Dark Secret", see Episode 4.Dark Secret is the second mission in Return to Castle Wolfenstein.
Having escaped from Castle Wolfenstein, B.J. Blazkowicz meets up with his Kreisau contact, Kessler, and infiltrates the town of Wulfburg. There, he discovers the entrance to a network of ancient crypts, which are being excavated by the Nazis in order to find the remains of a Dark Knight.
Unfortunately, the Nazis' meddling has unleashed ancient dark powers and awakened hordes of ravenous Undead, which attack anything in sight. Fighting his way through the crypts, Blazkowicz eventually reaches an ancient defiled church and faces the lethal Elite Guard squad, as he races to stop the Nazis from acquiring another ancient artifact - the Dagger of Warding.
There are five different parts of this mission. They are detailed below:
Part 1: Village
- Infiltrate the village.
- Locate the SS Paranormal Division's archaeological dig site.
Part 2: Catacombs
- Locate Professor Zemph's Journal.
- Pursue SS Paranormal Personnel through the catacombs.
Part 3: Crypt
- Navigate the catacombs to the Wulfburg Church entrance.
Part 4: The Defiled Church
- Infiltrate Wulfburg Church.
- Pursue Helga von Bulow to the ruined cathedral.
- Eliminate all of Von Bulow's personal "Elite Guards".
Part 5: Tomb