I can answer that very easily, and without writing a novel about it.
The heart lies within the thorax in the body. This location is called the mediastinum.
The heart is about the size of your fist and is located substernal, center thoracic, superior to the stomach with the apex on the left.
If you are going to write a novel, then do some research please.
Word of warning. If you are a medical student and preparing for an exam then do not buy this book thinking it will help, it will not.
Nor should you think that working in a hospital is anything like Scrubs, ER or any other show about doctors. You will soon realize that none of your colleagues are famous actors.
A Twat. Book Reviewer.