In Sabrina's belly, we were floating in a blood vessel. I checked the map of her body and assessed our situation. "Okay, so we can head along this artery and into her left leg, then we'll turn around and head back up this vein and eventually reach her heart, where we'll be able to take this artery up her throat and into her head... This could take a while..." Suddenly the bus was shook by something from behind. Large white blobs were latching onto the bus... antibodies! They were trying to destroy us!