Without more info it's hard to say, but from what it sounds like this is possible with a bit of creative styling.
Just to be certain, your goal is to have the content underneath the hero slide up over the hero when scrolling? Similar to this: http://musicrun.willwong.me/events/the-music-run-austin-texas
Note: the hero in the above link is not a fixed image - it is a fully functional slider with many elements inside it set to position-fixed.
If this is the sort of effect you're looking for, the read-only link is here:
If this is not the effect you are describing, can you please post an example of this that is live so we can take a closer look? (or detail out a frame by frame using screenshots)
Thanks in advance! Hope this help