I have since chosen to load a save and lead a different way.

At first though I was choosing to leave through the secret portal and I would come out in a tomb. There was gold on the ground and a note from someone for his spy in the mortuary (I assume its the zombie that wasn't). That was all fine but the whole area seemed to be sealed and I couldn't leave it. Or was I missing something?

As in kind of down and to the left? Damn I thought I had clicked everywhere and then gave up and started trying to attack different things with the crowbar. Thought I had to break the tomb open or smash down the bricks in the northern doorway. :D Thanks anyways. ;)

You're welcome. :) Yep, some locations' entrances and exits are hard to figure out, and you'll just have to scan the area.

I first entered this tomb from the outside, so I knew there was a door there. But, yeah, if you used the portal to get out, it must have been confusing.

That was also my main reason why I chose to leave the Mortuary by the front gate. I wanted to inspect the city first, and I wasn't sure where I might end up if I had went through the portal.