[spoiler][/spoiler]
I entered the hideout using the password and spoke to Zarys, giving her the Chest. However, she then ordered her goons to kill me as the chest had been opened, saying that she has told me not to open it. As this was the first time we had met, I'm not sure how she could have told me this. There needs to be some thought given to the possibility that the party may have a valid reason for the chest having been opened. The gnolls may have managed to open it before the party killed them and a dying Zhent asked them to deliver it. A persuasion check could be used to determine if this was believed.
Following on from the fight with Zarys, Ithen spoke to Oskar who told asked me to free him by buying him from Brem. As Brem was dead on the floor not 2 feet away from him, I would have expected him to realise he was already free, to thank me, offer a reward and then either run for it or ask if we could escort him somewhere.
Also, when speaking to Brem prior to the fight, he hints at being able to trade better goods after/if I get into Zarys' good books, but when you loot his body, he only has his standard goods plus anything you sold him.None of the chests contain anything that is much better, so not sure if I had actually delivered the chest unopened, if I would have been offered higher quality gear or not.