ABANDONED. man's wife was attacked in park and he shoots the attacker - time travel and alternate time stream

[Amy]

A man gets a phone call where the callers “You’ve had my wife for nine years and I’ve come to get her.” The man remembers that nine years ago his wife went for a walk in the park and was attacked. Someone shot the attacker and disappeared. The shooter was never caught.

Then the book switches to another version of the man. Nine years ago his wife went for a walk in the park, was attacked and killed. The man invented time travel and went back to shoot the attacker. After shooting the attacker the man realized he still remembered the attack so he must have created a new timestream. He then figured out how to get to the timestream where his wife was alive.

I read this book around 1980, I think. I think there was a swirl on the cover, but I'm not sure,

[Ayshe]

The Two-Timers seems likely?

[Kris]

No response, moving to Abandoned folder.

Amy (OP) was last active on the site in February 2020.