Here a bad narrative junction occurs. Vafrino cannot find out the exact nature of the conspiracy against Godfrey of Bouillon, so he goes on spying across the Muslim encampment until, all of a sudden -- "Fortune (what he himself could not do) untied the inner knots of his doubts" (GC 17: 61). And the episode ends like that, for now, without providing us further information.
This is one of the points in which the shift from Gerusalemme Liberata to Gerusalemme Conquistata spoils the result. In the Liberata (19: 65 ff), in fact, Vafrino sees Armida first, then Erminia, in the Muslim tents; and learns a lot by listening to the dialogs that happen there. Erminia, who soon recognizes him (she had lived as a prisoner among the Crusaders), asks him to bring her back to the Christian camp since she, though a Muslim, has fallen in love with the knight Tancred; and while asking so, she reveals the secret plot against Godfrey in detail.
In the Conquistata, however, Tasso reworks both female characters thoroughly. Armida 'officially' disappears from the stage at a certain point, even if it can be suspected that she 'reappears in disguise' as the Queen of Daphne (see posts titled "Is it her or not?"). Erminia in the new poem has a different name, Nicaea, and her story too is much modified. As a consequence, our 'private eye' Vafrino remains without either of his main contacts for his mission, and finally has to find a solution out of the blue.
According to many scholars, the ones who love better to parrot one another rather than read the texts, Gerusalemme Conquistata as a whole is a failure; a sorry, badly reworked version of the Liberata. This is simply false. The Conquistata is richer, bolder, more original, more modern, more interesting -- and to show it is one of the major purposes of this blog. But in this case, Tasso clearly did not feel like inventing some new, complex episode to replace Vafrino's meetings with Armida and Erminia. Never mind, Torquato, just keep enchanting us! ;-)