I adore Marlene and Seph interaction. ^^ It's so adorable, to think of Marlene ever being able to feel so at ease around Seph.

I'm thinking Zack is badly banged up, possibly unconscious from falling down somewhere/a bad fight/hitting his head/all of the above. And then Cloud was involved in the same events, but ended up with a serious fever, possibly resulting from falling in an icy stream or something such as that. So they may have been involved with Dalton and company, or else some other nuts working at Jenova Corp.