D&D 5E. Need advice on plot hooks and information.

Firstly just to clarify it's mostly the situation I'm stuck with not the actual plot. The party has allied themselves with a friendly ghost (It doesn't have the actual stats due to it being too strong but a much weaker variant) and it wants them to kill their uncle who happens to be a lord.

In actually it wasn't even the lord who killed them it was all just a plot to mess with the lord and try and make him weaker. I'm not necessarily sure how to use plot hooks and give small pieces of information instead of just revealing as soon as the lord died they have all been tricked and just pulling the rug under them in an unfair was like that.