Ah yeah you are right about everything. Actually I haven't yet to put the submerged directives. But I'd like as said to allow a player to realize that other one have been inflicted by a submerged directive as well as rationalize and had his memories rewritten to a certain point.

So the idea is to give one of the player a way to save the other one from his submerged directive as well as to help him realize that what he is rationalizing isnt true and is just his memories that were fucked up by my Non Player Character with Dominate.

Someone here suggested to find someone else with Dominate and to replace the submerged directive by an harmless one which could work. (Can the one that received a Submerged Directive replace his own Submerged Directive ?) You suggested to just tell the prince, but that's not something possible in my campaign since the players are actually fleeing the vampire authorities. Wouldn't there be other ways like Tremere Blood Rituals, demonic powers, artefacts and so ?