Tony and Mark have an interesting relationship. They are close but not close enough that Mark knows Tony's ex-wife, and not close enough that Tony knows Mark's fiancé. It's a clever story, overall.
Here's a tip for you: Consider adding some dialog between your characters. It really helps to bring the characters and scenes to life.
The Ink Well has some great resources in our catalog of fiction writing tips. For example, we have tips on developing characters in your stories, and integrating action, dialog and narrative. We also have a great article on using Google docs to find grammatical errors in your story, called Help for the Grammatically Challenged.