It has been a long time since I've read a story so good that I just had to post! One of the reasons I can never actually quit this place is, once you get past the poisonous stuff, you can find some damn good stories and some pretty consistently good writing. I personally loved this story. Developed the characters decently and built the plot up well. And threw in some nice twists.
I agree with those who mentioned the motorcycle ride as a point where the story takes an egregious turn towards the bizarre. And I just loved this point in the plot because it really made me take sides between the two characters.
The husband character is not likable whatsoever and I was inclined to root for the wife character...until the motorcycle ride.
Let's lay out the facts provided:
1) She has two children.
2) She already knows motorcycles are dangerous.
3) This. Guy. Has. Recently. Crashed. His. Bike. And. The. Wife. Knows. That.
Doctor mother of two kids plans to ride on the back of a stranger's motorcycle despite knowing motorcycles are dangerous and this man has recently crashed. The subtlety with which you present such an absurd plot point is just wonderfully done.
Anyway, the wife character's intention to go on the motorcycle ride is a greater betrayal of trust than any emotional or physical affair, and that is the point where the husband character needs to draw the line because the wife character dying would have the most significant negative effect on their children.
I suspect the second act of this story will be the hiring of a P.I., discovering the worst depths of her betrayal including a plan to cut you out financially while keeping the daughters and the eventual lawyering up. Act 3 will be the bitter divorce proceedings where the ex-husband wins. Act 4 will be life after divorce where the ex-wife enters an official relationship with her biker paramore, ex-husband goes into teaching full-time while gaining full custody of the daughters, but lives a lonely life. Final act is the reconciliation where the biker paramore either leaves the doctor ex-wife for a better woman or dies in a bike accident, ex-wife comes back on hands and knees, weak male ex-husband accepts her, daughters grow up bitter about love and hateful of their mother.