i found all the opus pages but number five...assuming there is 8 in all. anyone have any idea were i might find it in the soul cairn?

Theres 10 not 8 & try looking up the UESP or something.

thanks ill try that...

Or you could just keep looking yourself, do it the hard way, more satisfying than, looking it up.

There is also a skeleton of an adventurer there somewhere, with his little note, but that is not a "quest". It is always best to look yourself rather than rely on looking for answers, could be all sorts of interesting things and contraptions in there.