Jeremiah Healy 
Right to Die [EPUB ebook] 

While guarding an activist from an assassin, Cuddy makes himself the target To impress his girlfriend and remind himself of his long-neglected athleticism, John Francis Cuddy is training to run the Boston marathon. But the private detective’s fitness regimen goes on the back burner when an old friend approaches him with a dangerous assignment. Euthanasia advocate Maisy Andrus has been receiving death threats, and the police are helpless to protect her. As he tries to keep the crusading lawyer alive, Cuddy realizes that the question isn’t who wants Andrus dead, but who doesn’t.Protecting the right-to-die advocate dredges up painful memories of Cuddy’s wife, who died a slow death from brain cancer. The closer he gets to unmasking the would-be assassin, the more his old wounds open. When the killer starts taking potshots at him, as well as his client, Cuddy’s marathon training will come in handy.