1. Yargos replicates the codes on a lark. Why on earth would he do this? And what happened next? Did the Black Echelon destroy the bell towers?
2. Yargos then tries to alert the city. I take it nobody believed his story? If the bell towers were destroyed, why didn't they believe him?
3. He then tries to hurl the codebook into the sea. However, Nessian "intervenes". How exactly did Nessian learn of the book and how did he intervene?
4. Nessian later sends his goons to kill Yargos. Why didn't he kill the historian immediately?
5. Act 1 starts at early evening. Act 4 at sunrise. Since the PCs are under time pressure, I assume they didn't sleep. Where did the time go then? Surely act 2 and 3 don't take all night to complete?
6. Nessian plans to blackmail the city. However, it is made clear that unless the abort code is given within half an hour of the cathedral attack, the city is doomed. So how exactly does he plan to go about his blackmailing in that short timeframe?
7. For that matter, is it wisdom to be encamped just outside the city when you summon an army of undead to sack it? :-)