Gamers With Jobs has written up an article entitled "Planescape: Torment Revisited", in which they delve into the game's story-telling ability and offer their thoughts on why it was second to none. A snippet:
Upon touching the stone labelled "Longing", you are shocked to realize that the memory imprinted upon the stone is that of the woman Deionarra. Even more shocking, the memory is of her conversation with your prior incarnation! Since you're experiencing this conversation through Deionarra's perspective, you are fully conscious of her feelings. You sense that she is in love with your former self, that her commitment is complete and undying. As you observe the conversation, your lost memories begin to return, and everything falls into context. You remember that you were preparing to set out on a dangerous journey, and that Deionarra wished to accompany you in spite of the peril. And then you realize: you wanted Deionarra to come with you, in order that she might die.
As the memories wash over you, the cruelty of your former self becomes apparent. You used to be a cold and calculating man, brutal and evil to the core, and your relationship with Deionarra was built upon lies in the hope of luring her into a trap to suit your own nefarious purposes.