William isn't only in this for the revenge. The idea of watching Ben's already soft body grow under his own touch is darkly appealing to him. The revenge, and Ben's own resistance, are just icing on the cake. Together, William and Greg plan for the event. Ben goes to the shower at odd hours. It's late in the morning, when everyone else is already gone. It's probably so that nobody can mess with him in the shower, but since William and Greg share a morning off once a week, it's perfect for their plan.
They prepare early in the morning. Greg performs the spell quickly and transfers all of his fat to William. William feels the warmth again, spreading throughout his body, but the prolonged exposure gets hotter. He feels himself sweating and this time watches the fat grow over his body. Remembering the tightness in his clothes last time, the boys had the foresight to wear untied robes this time.
The 20 lbs from their previous encounter return, and William, with even less height than Greg to spread it over, develops the beginnings of a belly. He feels his front half sag quickly, like sand is being poured into a bag over his shoulders. He feels his ass grow too, more cheek touching cheek as the buttocks expand. He wonders if it's the magic or the fat that's turning him on.
20 more lbs pass from Greg into William and the belly is growing even more. It has a soft weight to it, and begins to push the sides of the robe apart. When William moves to close it again, he notices that even his arms feel heavier. They are softer and hang more as he pushes the robe together again, and tight. His thighs, too, begin to touch and continue to do so as the weight pours on.
The final 30 lbs pour onto William's body and he is barely recognizeable. 70 lbs heavier than he was 5 minutes ago, William's belly can barely be held in even by his robe. It is topped by manboobs, with nipples considerably larger than before. His thighs grip each other in sweat. The whole process has made him hot and sweaty. William raises his hand to wipe his brow and notices that even his hands have changed and are pudgy.
The boys break contact. William looks over at Greg and is terrified. Greg, drained of all his fat, is dangerously thin. There is little muscle tone to speak of, and so even under robes it is easy to tell that Greg is unhealthily thin. Greg seems to notice it.
"Guess I'll have to put some of that back on. Shouldn't be too hard, and maybe I'll do it the natural way."
He pats his belly, or where it was, and winces, forgetting there isn't padding to absorb the blow.
William feels uncomfortable in his new body, even temporarily, and decides to take a shower. Greg reminds him that he only has a half-hour before the change becomes permanent, but William waves him off.
In the shower, everything feels different. William's taken showers before, but never like this. There's so much more of him to get wet, to massage, to soap up and enjoy. William rubs himself all over and takes full advantage of the hot water on his belly. He finds it particularly gratifying to grab his ass with both hands; a much fuller task than before. Before he knows it, Greg runs into the bathroom and shouts "You've only got 30 seconds left!"
William panics. In the space under the stall wall, he sees another guy's leg. He can't tell who it is, but he could transfer the fat to them in the time remaining. Or, does he try to run and give it back to Greg?