Well I've gotta say I didn't expect this to be the ending but it's a good surprise, I like surprises, and in terms of what could have happened to Gerard I have no clue. Maybe if he hadn't found Kel and Trent yet he might have suddenly found a lead so went to find them, or he did find them and they did something to him, I'm not sure but those are my two possibilities.
Anyway, in terms of a sequel I think one would be nice but not really necessary, you could end it at this easy because this is a good end as it is, but the choice is yours at the end of the day.
I really liked this story and it's not too often I actually follow them to the end so congrats on a great story. =D
BTW Sorry I'm late to review but I've been staying at my Nan's lately and she has no internet, how I've survived I have no idea lol.
S xx