Secrets of the Ark (The Angel of Death in the UK) is the fourth game in the Broken Sword series. It is the first not fully developed by Revolution Software Ltd. Instead, they outsourced the art and programming to Sumo Digital Ltd., which already provided consultancy on the PS2 and Xbox version of the third game, The Sleeping Dragon. Charles Cecil still wrote the story and oversaw development however. Unlike the previous game, it is now only available for the Windows platform.

Keeping to the tradition of ancient mysteries, hero George Stobbard needs to expose an old rivalry between powerful factions as he chases after a manuscript Moses used to construct The Angel of Death. This powerful weapon was the final of the ten plagues that brought the Pharaoh to his knees and allowed Moses to start the Exodus as he freed the Israelites from bondage in Egypt. The factions are especially interested in the mysterious substance "mfkzt", referenced in the manuscript but forgotten for thousands of years.

George gets involved when he is forced to take a job at a bail bonds company in a dangerous neighbourhood. The Dragon incident is classified as mass hysteria and he has been blacklisted by his previous employers. During one of his assignments, he meets Anna Maria who tells him about the manuscript. As she is being chased, George decides to help her. The familiar French reporter Nico Collard is also present in the game and this only complicates things as George has to keep the balance between the two women. Some of the locations you visit include Phoenix, Vatican City, New York and Istanbul.

Although still relying on a full 3D engine with fixed camera perspectives, the game returns to its roots by reintroducing point-and-click-based mouse control next to keyboard control, along with a new drag-and-drop control mechanism. A few puzzles are still action-based, but you are now given more time to act in stressful situations, rather than having to make split-second decisions. Next to the regular puzzles, you need to investigate images, texts and clues in the central manuscript as the story progresses.