Lost in transformation

Tommy's transgender spell works like magic
Tommy desperately turned the pages of the spell book. The reverse spell had to be there, and he needed it fast. His wife was downstairs waiting for him and if she came up and found him like this he didn't know what would happen.
The idea had come to him when he was browsing in an old bookshop. Tommy had been crossdressing in his wife's clothes for years without her knowing but he always wanted to know what it would feel like to really be a woman. Then he noticed one of the shelves had some spell books on it. Tommy searched through them and sure enough, in one old, tattered book, he found a spell for 'Becoming the woman of your dreams'. He didn't hesitate and bought the book.
The spell itself was fairly easy to perform and at the first opportunity he got when his wife Claire was out he tried the spell. A little bit of this, a little of that, some feminine incantations and Tommy felt his body bulge and contort in the most bizarre way. It didn't hurt, but he felt as though he was bubbling all over. The sensation increased and he began to loose consciousness. When he finally woke up he could feel the difference immediately. His hair was long and flowing, to his chest had filled out to form a perfect bust, his hips were curved and his butt perfectly round. His skin had lost all of its hair and was now soft and smooth. But more than that he felt like a woman. Never could imagine such a wonderfully feeling, so feminine on the inside and out. He rushed to Claire's cupboard and began trying on her clothes. He pulled on a pair of cotton panties and at last he truly understood why woman enjoy pretty underwear. He felt so cosy and comfortable it made him squeal. He found a matching bra and admired his new looks in the mirror.
Then he heard Claire coming in through the front door. He must have passed out for longer than he imagined. Tommy grabbed the spell book and frantically began looking for the reverse spell.
Downstairs Claire was calling up to him to ask if he was okay. He nearly replied but then remembered his voice had changed. He would find the spell, get into bed in case he passed out and pretend that he had fallen asleep.
At last he found the spell 'How to revert to your former form'. The spell was short, only three simple-looking steps. Tommy breathed a sigh of relief and quickly scanned the instructions. His heart plummeted when he read the third item in the list:
'Drink the glass of water containing a drop of blood from your original body'...