Single Player Walkthrough
-By Thrrrpptt! and Sluggo

Note: This guide is not accurate for the Xbox or PlayStation 2 versions of the game! Some similarities exist, but this guide is not intended for use with those game versions.

Skip to a specific Mission:

Mission 1: Ominous Rumors
Mission 2: Dark Secret
Mission 3: Weapons of Vengeance
Mission 4: Deadly Designs
Mission 5: Deathshead's Playground
Mission 6: Return Engagement
Mission 7: Operation Resurrection

Mission 1, Level 1: Escape

You and Agent One are captured and locked deep within a dank German castle. You must escape from your cell, fight or sneak your way through the prison's lower regions, and make your way to the surface. Any information or Nazi treasure that you can find along the way will be most useful.
Mission 1, Level 2: Castle Wolfenstein

Continue your flight from the castle, fighting your way through entire platoons of Nazi soldiers. It is imperative that you make good with your escape so that you can meet Kessler, your contact in the German Resistance circle known as Kreisau Circle. The information he has on the SS Paranormal division is of great interest to the Allied forces, and it's up to you to collect it.
Mission 1, Level 3: Tram Ride

Ride the tram to freedom, finally escaping the German prison where you and Agent 0 were captured. The scenery is beautiful, but you'll meet heavy opposition so don't spend too much time admiring nature's handiwork. At the end of the ride you will enter the village where you meet Kessler. This member of the German resistance group will aid you in your quest for information, so you must find him.
Mission 2, Level 1: Village

Helga Von Bulow, the head of Himmler's SS Paranormal division, is overseeing some kind of mysterious excavation near Castle Wolfenstein. You must uncover what she is up to, relying on help from another member of the Kreusau Circle, Karl Villigut. This operative is waiting for you in the village and has an item critical to your mission.
Mission 2, Level 2: Catacombs

Your pursuit of Helga Von Bulow has led you to the catacombs that snake beneath the village. At the other end of these dark passageways is the entrance to an old abandoned church where Von Bulow and her cabal of Elite Guards are excavating. Rumors of terrible creatures prowling the catacombs fill the beer houses in the village, but you must delve into them if you want to stop whatever Von Bulow has planned.
Mission 2, Level 3: Crypt

Your macabre adventure into the catacombs beneath the village has taken you deep within the earth where supernatural terrors make their lair. The catacombs are also full of traps to make short work of foolish visitors, but that's the least of your worries.
Mission 2, Level 4: Defiled Church

Surfacing from the catacombs you find yourself in the middle of a 1,000 year old church that has long been defiled and made the home of many dark rituals. Helga Von Bulow is here now, along with her personal guards. These Elite Guards are highly trained and bound together by a witch's coven, so they are the most dangerous enemy you've faced yet. Be careful.
Mission 2, Level 5: Tomb

Von Bulow's prize is finally within her reach. The Dagger of Warding is an artifact of immense supernatural power, and this woman will possess it at any costs. But what might be guarding the dagger? You're going to find out.
Mission 3, Level 1: Forest Compound

Deathshead aims to release a chemical ordinance on the Allied forces via a long-range rocket. He must, obviously, be stopped. You'll have to infiltrate his rocket base armed only with a knife and Sten. This mission requires to you to collect the experimental Snooper Rifle and stow away in a supply truck.
Mission 3, Level 2: Rocket Base

Deathshead's rocket is primed for launch, pending a few final tests. You must make your way to the rocket control room to activate the self-destruct mechanism before the deadly payload take flight and heads straight to London. The base will, of course, be heavily guarded.
Mission 3, Level 3: Radar installation

Tha Axis are experimenting with a new kind of aircraft code named "Kobra". Your mission is to steal one of these crafts from right under the noses of Himmler's own "Black Guards" and bring it back to Malta for examination. While you're at it, you will need to locate and destroy the MVX-mk1 Radar to cripple the Axis intelligence in the area.
Mission 3, Level 4: Air Base Assault

The Kobra is almost within your reach. You only have to eliminate the last few lines of reistance and prep the ship for launch. But beware: The Black Guard are likely to become aware of your presence in the airbase and move to stop you.
Mission 4, Level 1: Kuglestadt

The Axis plots are beginning to become more and more nefarious. You are now reasonably sure that they are involved in some kind of research involving advanced robotics and the occult, but it remains unknown what their exact goals are. As the first step in undoing their work, you must infiltrate their secret labs. One of Himmler's top scientists wants to defect to your side, but remains captive in a bombed out city under siege. You must accompany a Panzer tank through the war-torn town and help the scientist escape.
Mission 4, Level 2: The Bombed Factory

This new area is thoroughly ravaged by Allied bombing raids, but still contains many dangers. You will have to pass through this tattered industrial complex on your way towards Himmler's X-Labs. While you are at it, you will need to secure another critical intelligence item: The technical notes for a new type of machine gun called the "Venom Gun".
Mission 4, Level 3: The Train Yards

The last area between you and the X-Labs is an old train yard concealing many dangers. This area is relatively untouched by the bombs of your allies, so it is still well guarded. Somewhere in this area lies the hidden entrance to Deathshead's laboratories.
Mission 4, Level 4: Secret Weapons Facility

You've finally made it inside of Deathshead's Secret Weapons Factory. Now you must pursue Deathshead to his secret submarine pen and find out what you can about the location of his mysterious X-Labs.
Mission 5, Level 1: Ice Station Norway

Your interrogation of the Axis captive has revealed the X-Labs' position: Norway. Lightly armed but ready for anything, you must fight your way through the icy terrain and punch through the compound's outer defenses.
Mission 5, Level 2: X-Labs

You have located the entrance to the X-Labs, but what you find within may make you wish you hadn't. Your goal here is Deathshead's personal project book, which should help you unravel the dark mysteries surrounding this place. Be prepared for anything, though, as the madman's most dangerous creations are sure to be found here.
Mission 5, Level 3: Super Soldier Chamber

You have cornered Deathshead in his Super Soldier lab, but he's not alone...
Mission 6, Level 1: Bramburg Dam

Deathshead has fled and his location remains unknown, but that's the least of your problems. His project book tells you that he and a witch priestess known as Marianna Bavatsky were planning on using the last of his cybernetic terrors to resurrect Heinrich I from his grave near Castle Wolfenstein. They must be stopped. You are to be airdropped a few miles outside of the ceremony's intended location, and must make your way there. The first obstacle in your path is the heavily guarded Bramburg Dam.
Mission 6, Level 2: Paderborn Village

Your journey to the ceremony site takes you through the village of Baderborn, where several of Himmler's paranormal experts are gathered. Not one to let such a golden opportunity pass by, you must assassinate all of these generals before finding your way to the chateau.
Mission 6, Level 3: Chateau Schufstaffel

This large mansion must be breached in order for you to gain access to the ceremony site. Fight your way through and find the back door leading to the woods behind the building.
Mission 6, Level 4: Unhallowed Ground

You're drawing closer and closer, but first you must cross the dangerous forests between you and the ceremony where Bavatsky is planning on resurrecting Heinrich. It's not going to be easy, as more of the Elite Guards will be on hand to stop you.
Mission 7, Level 1: The Dig

Delve deep into the ceremony's excavation site on your way towards the ultimate confrontation. Once you find the site, you must destroy all of the Super Soldiers that are guarding it.
Mission 7, Level 2: Return to Castle Wolfenstein

Fight further through the dig site, drawing ever closer to your goal. Here you must battle more undead and locate an alternative entrance to Castle Wolfenstein if you are to stop the ceremony.
Mission 7, Level 3: Heinrich

Finally, the end is near. But will it be your end as well? Bavatsky has succeeded in bringing her master back from the grave, and you're in for one hell of a fight. The future of the world lies in your hands.