Your storyline's good, some things need to be changed though as they seem unrealistic. Like when Sage kills Riley's mom, they end up laughing, he doesn't seem sad at all at the loss of an important family member. Also, Riley sounds a bit feminine, even though he's young, he shouldn't keep wining like that and getting scared out of his wits when the other girl has the guts of iron. That's about it, there aren't any major flaws in your story, just some minor errors which I'm sure you can improve upin! :-)
Ceeya around!
*Rock&Zombiez!*
-Vz-