What the hell is going on?

One minute Robert was sat on the train travelling home from a hard day at work and the next he found himself bent over the hood of a car being taken from behind by a well-endowed man or so it felt to him as he felt something sliding in and out of him.

He found it so hard to speak with the man pounding away energetically so it was not until the man had emptied himself deep inside of him that he discovered that he was now in the body of a woman who loved dogging in the local woods and  was able to let the man know something was up.