The concept is presented in a flurry of facsimile documents that set the scene and create the right atmosphere even before we reach Part 1: Introduction, which explains what 'World War Cthulhu' is all about. Basically war presents opportunities for the followers of dark forces, and the major distruptions of the last century and in particular World War 2 gave rise to unprecedented scope for them to push forwards their plans with little risk of detection. The World War Cthulhu line is intended to explore other avenues as well, but with this the first book in the series the intention is to look at Europe in the early part of the Second World War. It's Allied-centric, with the party involved in defeating Nazis and Mythos creatures alike, although interestingly the Nazis are not represented as attempting to harness the Mythos in support of the Third Reich. Despite Nazi activities in the realms of the occult, they are still not quite that insane! The default setting is that they belong to Section N, an intelligence network - if nothing else, it's a good vehicle to send them off on missions!
The rest of the Introduction sets the mood of the game and details British Intelligence in considerable detail. It's likely that recruits to Section N (which comes at the end) may well be drawn from or at least familiar with the other organs of British Intelligence. If you have a burning desire to play an American, remember you'd be a volunteer in a British unit... the USA is yet to enter the war at this point!
Next is Part 2: Investigator's Resources. Character generation is based on the Call of Cthulhu ruleset, but it's advised that you use this rather the the core rulebook as these characters will be honed to withstand the rigors of wartime. If you do want to use an existing Call of Cthulhu character, there are some notes on how best to tweak it to suit, however. One difference is that the character's background is split into a pre-war occupation and the military service undertaken (in total war, even civilians get swept up in the war machine). As well as noting how the character became aware of the Mythos, recruitment by Section N is also covered - and the resultant training may yield some useful additional skills. As well as British characters, there's information about those from Australia, New Zealand and Canada (the Commonwealth having joined the UK in the war from the outset), escaped Europeans (especially from France and Poland) as well as a word on Americans. After all the detail you need and a worked example, there are some new occupations - politician, scientist and spy - and some new skills suited to this particular environment.
The rest of this chapter moves on from the game mechanics of character creation to a discussion of Intelligence Operating Procedures. Standard procedures can be a blessing and a curse: understanding them can stop you making a silly mistake but following them blindly can lead to disaster or detection. Study them well and use them wisely. For those intending to play military-oriented characters there is also an analysis of small unit tactics. Even the non-combatants ought to read through them - incoming fire rarely stops to ask if you are a trained soldier! Both these sections provide a solid overview of the matters under discussion and are particularly useful for players who have minimal experience in espionage or military combat.
Part 3: Keeper's Handbook covers all manner of things that the Game Master or Keeper should bear in mind when planning or running their game. Whilst there is a lot of good advice here, the main gist of it is to pile horror upon horror, playing to the 'purist' mode of Call of Cthulhu which aims to be as realistic and gritty as possible. The fight against the Nazi horde should be rooted in reality: draw on documentaries and history books rather than movie interpretations. While the agents of the Mythos might be taking advantage of all-out war to further their own ends, N - the party's director - is also taking every advantage of his position in British Intelligence to further his own war against the Mythos. N sure knows a lot about the Mythos, too. Here you can read a fair bit about his background and perhaps discover who he actually is... something the characters might never know, or may discover if (when?) they have to step up and take his place. Several suggestions are made, select the one you prefer or make up one of your own.
Moving on to a discussion of builing plots, things get complex with many strands - human, Mythos, the 'mundane' course of the war - to weave together to create each adventure. Standard intelligence missions are often subverted by N to his own ends, but the needs of the war and maintaining his cover means that the intended mission aims must be met as well as N's own. Then there are the plots being perpetrated by Mythos agents to defeat, as well as said agents to investigate. There's a lot going on, a lot to keep track of... and that's before you get to the strange places and alien horrors that also need to be investigated! There are some maxims for running adventures too. Make things personal - no nameless mooks amongst the opposition, for example. The Mythos and the war effort don't mix: this is not an alternate-history 'weird war' but the Mythos intruding into the real world. It's best to avoid big battles and too many encounters with historical figures, however - you don't want to introduce opportunities for history-changing events. There's a lot to think about as you plan.
Next comes a survey of theatres of war, with suggestions for missions that can be run in each one. Plenty of historical detail mixed with more outlandish stuff here, ready to spawn ideas in your mind for plots. Many mission suggestions have to components: an intelligence mission based on British war aims and a secondary mission at N's instigation. This is followed by The Dark Lamentable Catalogue, which documents Mythos cults and the Mythos beings whom they serve.
Of course, Mythos cultists are not the only opposition, and Behind Closed Doors presents some of the murky organisations, committees and people that the party will have to navigate and contend with back home in London. Attention then turns again to small group tactics, the focus now is on running encounters to best effect. Although it's best to stay away from pitched battles, there's enough here to enable you to run them well if the party's involvement is unavoidable. Should the adventure go underwater, there's information on SCUBA equipment and the underwater environment. Excitement can also be supplied with sections on parachuting and other military skills. Aerial, naval and vehicular combat is aslo covered. This is followed by the Equipment section, which pays attention to the difficulty of obtaining things due to rationing and black marketeering in different areas of Europe. There are plenty of weapons here too, even if their use against Mythos creatures is limited. They don't come with pricetags, they will either be issued or stolen...
Finally, The God in the Woods presents a complete campaign setting with scope for plenty adventure. It's the small town of Saint-Cerneuf-du-Bois in the Dordogne, which lies close to the border between the Nazi-occupied territory and Vichy France. There's a lot of information on locations in the town and the surrounding area, what is going on there, and a whole host of NPCs to encounter there. Everyone is well-developed, with a character and personality all their own. There is, however, Something in the woods - and a group dedicated to it. Once this introductory background material is presented, the sequence of events to drive your campaign is laid out, beginning with a briefing in London... and running over several weeks if not longer, with scope for side-missions and a myriad of events to throw in at opportune moments. It's a delightful slow unfolding of unspeakable horror lurking in the woods and blighting the whole neighbourhood.
A character sheet and a wonderful collection of strange snippets, events that are claimed to have actually happened but are weird enough to form the basis of future adventures finish up this book. What's really appealing is that it mixes real-world history with the Mythos, pulling no punches with either yet avoiding descent into a weird alternative history where the Mythos affected or was harnessed by the conflict going on around the party.