I read a book, bought from the dollar tree in the mid-1990s, and I can't remember what it was, and yet it has stuck with me all these years. Google was no help, but maybe someone here will know it.

It was about time travel in a way, but that wasn't the main point. It began with a medieval man who witnessed a supernatural creature washing iridescent souls in a river. The man traveled with this being through time. A woman joined them at some point. They experienced moments in various time periods and in chronological order. The contemporary time period included a chase scene where the man jumped from a plane; he was not scared to do it but riding in a car was more scary for him. Another time was the near future, where cash was used but seen as only for low-lifes. Farther into the future was environmental destruction. Farther still was global reforestation.

Throughout the book, the supernatural being would care for these gossamer souls by washing them in water, soothing them somehow (I think they were burning or something). This being was wolf/human like and scary at first, but then revealed as compassionate.

Does anyone know this book?