Neat, but a few small things...
You did a good job with your camera movement here and the motion is nice and fluid, but I have a few little things to say. If the grey character following the guy is his shadow, make sure it stays behind him unless it is shown that the light is in the center. Also, it would be good to see the shadow work in conjunction with the surroundings, e.g. in the beginning where the character enters, the shadow should not appear on the door. Instead, it could be transitioned upwards where it is on the door so it looks like the door is actually popping out (or not on it all together).
Second, the stairs look a bit messy. I would recommend that you draw them using a grid made of the markers or by using a layer with lines on it that shows the movement of the stairs. They look neat, but can be distracting if not done neatly. ;)
Third, a little shading would be a neat addition and would add to the realism of the scene. You have a little bit of shading on the stairs in the form of gradients (which you used very appropriately in my opinion, which is something very hard to do), but some very light shading (or at the least, very VERY slight gradients on walls or such) would add a little bit to the realism.
Generally, just keep on practicing, it looks good, but I am sure you can make it even better! :)