Musically, the most famous moment in Puccini's opera Turandot is the aria Nessun dorma, 'nobody sleeps', in which prince Calaf explains in jubilant tones that in the morning he will conquer the heart of princess Turandot. One reason for the aria's great dramatic power is the contrast of the prince's exuberance with the despair of the choir, which sings: "No one will know his name and we must, alas, die." For Calaf has made a deal with the princess. He has answered all three of her riddles correctly, and therefore she must marry him. But, he has told her, if she manages to find out his name by dawn, he will gladly die. And thus the princess is searching for his name and she has threatened everyone with death unless they help her succeed. But only one person knows his name: the slave girl Liú, who loves Calaf and would rather die than reveal it...
The Fourth Riddle takes place during this aria, but instead of seeing the world from Calaf's perspective, we step into the skins of the two female protagonists, Liú and Turandot. This is a brilliant take on the opera. We know that Calaf is somewhere out there pontificating about his impending victory, but in fact, in this particular rendition of the story, his fate will be decided when he is off-stage, by the interactions of the two women in his life -- the one whom he loves even though she does not seem to deserve it, and the one whom he does not love even though she most certainly does deserve it. It is Liú especially, poor Liú, who is treated with condescension by almost everyone in the opera including, arguably, the librettist, who finally takes the reigns of he own fate and becomes more than a splendid self-sacrifice. Even if she does end up sacrificing herself, at least we know that she had more paths to choose from and that she seriously considered them. For that's the kind of game we have here: a relatively linear main part, but with a wild branching of endings based on choices at the end.
As a game, it's all enjoyable enough. There are some mild puzzles here that will not stump a moderately seasoned player of IF. We get a chance to experience the palace and see something of the emotional state of the two women. In the end, they are not truly drawn as characters, in part perhaps to leave open all these different endings. But that's fine. The Fourth Riddle is not a deep psychological reinterpretation of the opera. Rather, it is a pleasant exploration of some alternate possibilities, a variation on the original theme, some relatively good-natured fun with a classic work. Recommended if you know the opera; probably too baffling if you don't. (In which case: go watch it.)