Because I used the Keep on the Shadowfell adventure hook my PCs went to the trading post as soon as they got to the seven pillared hall. After the trading post but before they investigated the horned hold they went to the chamber of the eyes per the tip from Rendil. I used that time they were away, and the night they spent in the Halfmoon Inn once they got back from the chamber of the eyes as time for an investigation by the Ogre, Orontor, and the enforcers.
I had it play out such that Gendar the drow (first book page 14) was a witness. Since he has his own problems with the durgar he intended to enlist the help of the PCs, first with the threat of exposing their presumed crime, and if that didnt work then with a simple payment for services. He tracked them down to the halfmoon inn and waited for them to wake when the Ogre and Orontor found him.
Through their investigation the enforcers found out that Gendar was a witness. It just so happened that when they choose to confront him is when Gendar was waiting to confront the adventurers. As the adventurers came down to the common room in the morning, they saw the Ogre and Orontor interrogating Gendar. As Gendar saw them he broke and told the Ogre and Orontor what he saw, implicating the adventurers.
Orontor then made his way towards the PCs and after a little chat it came out to if the PCs investigate Paldemar, their problem with the traiding post would go away. The PCs agreed, and after this little bit about trying to find the slaves in the Horned Hold and looking for Gendars staff (he hired them after their encounter with Orontor, as his false threat of offering further incriminating evidence failed), they (probably) intend to look into Paldemar.