Secret Files:Tunguska is one of a growing number of ports of successful PC games for the Nintendo DS. Having already played and enjoyed the PC version, I had my doubts about how the DS version would measure up, so I was pleased to discover that it is a good example of how well these ports can work on the handheld, providing an enthralling adventure in the palm of your hand. In fact, it may even prove a more satisfying experience for first-time players thanks to a few enhancements and the removal of most of the questionable voice work that took the edge off the original.

For Secret Files newcomers, the story is (very loosely) based on the real historical event of June 30, 1908, when a Siberian mountain range was devastated by an unknown object colliding with the earth. The force of the impact was greater than 2,000 Hiroshima bombs and flattened the surrounding area as the vibrations literally shook the earth and lit up the night sky across Europe. In the game, the cause of the blast remained a mystery until fifty years later when Vladimir Kalenkov staged an expedition to investigate the phenomenon, but his findings were published in a report that was suppressed by higher powers. Thirty years later, Kalenkov is busy with his job in a natural history museum, his research long since left behind, if not forgotten. That is, until he is kidnapped by a mysterious cult who appear to be interested in his discoveries. This is a case for Mulder and Scully, perhaps, but instead the trail is taken up by Kalenkov’s daughter Nina and a museum worker named Max on a globetrotting adventure that takes them to Russia, Ireland, Cuba and China.

At first glance the game might look like a clone of Broken Sword, but the further you proceed, the more the plot develops its own distinct character. While it isn’t entirely cliché-free (boy helps girl, guess what happens), and comparisons could be drawn between Secret Files and other conspiracy-themed adventures, the story details and characters are just deep and different enough for this not be an issue. Nina’s motivation for finding her father comes across as genuine concern rather than an excuse for an adventure gaming frolic, creating a dramatic story spoiled only by an occasionally-misplaced sense of humour.

The two main characters are playable at different points during the game. When it’s possible to switch, an icon appears onscreen, and tapping it with the stylus shifts the scene between Nina and Max. Most of the time the player will be in Nina’s shoes, but there are times when you are able to play either one as they experience separate adventures, and one section allows you to play as both cooperatively, alternating between them to overcome the shared hurdles set before them. While you’ll still need to perform each protagonist’s tasks in their entirety, the dual character control means that if you get stumped at one particular part of the game, you can always switch to the other character to make progress in a different area in the meantime.

As well as Nina and Max, there are many other interesting characters you will come across, as the game has quite a large supporting cast. There is of course Nina’s father, the natural historian with a shady past, an evil billionaire, a grouchy Irish barman and a Russian train driver who has lost his keys down the toilet. The game is mainly serious with some comedic touches, though at times the silly jokes take something away from the intriguing storyline. The absence of character voices during the playable part of the game is an improvement over the uneven performances of its PC predecessor, although some of the cinematic video sequences do feature voiceovers, which add to their already impressive quality.

Conversation in Tunguska is presented in speech bubbles on the top screen as you tap the bottom screen to move to the next line of dialogue. This manual control is a good thing, preventing the text from moving too fast on its own and causing lines to be missed. In the movie sequences, the dialogue can whizz by a bit too quickly, but it’s really only in the opening cutscene that this can be irritating, and all clips are viewable after the game is completed. The dialogue itself remains intact from the PC version, and it still contains some issues with the translation from its original German, as some sentences sound a little odd or out of context and some of the humour doesn’t translate well.

Throughout the game, entries are added to a diary-like feature which logs key events, although it does so as an outsider rather than a first-hand account of Nina or Max. It also serves to deliver an introductory message on the mechanics of how to play when you start a new game. This is a shame, as it breaks the excitement built up from the opening movie and isn't really necessary.

Visually, Tunguska successfully manages to capture the high quality of the PC original, displaying 2D backgrounds with 3D character models. The environments look great even on the tiny DS screen, packing a good amount of detail into very well rendered and realistic backdrops. Locations such as an Irish castle and a remote research station in the middle of a frozen wasteland represent a couple of the more diverse areas you’ll explore in your travels. The amount of detail can be a drawback at times, as some objects are nearly impossible to see, but thanks to the help of a hotspot highlighter (which was often helpful in the PC version but practically essential here) this isn't too much of a stumbling block.