Did you finish off both thugs? They each drop keys for a couple locked chests. There is also a letter on the table there you need to take and then speak to Marcus about.
If you didn't take out the thugs, there shouldn't be a problem waiting until you have leveled up a bit, have better equipment / spells, or more restoration potions.
Marcus-Tingalf-Trevor-Quest (spoilers)
Welcome to the forum.
