Playing StarCraft 2 HEART OF THE SWARM for the FIRST TIME!

I really really loved the Wings of Liberty campaign for StarCraft 2; so much so that I beat it within 50 hours! I just couldn't resist starting the next campaign, Heart of the Swarm! Who knows what will happen now that Kerrigan is cured. How does she get infested again? Why does she get to control the Zerg again? And what about Mengsk? He ordered Tychus to kill Kerrigan, and now I think he'll try to do it himself. We'll find out!