When disgraced banker gets a job working as a truck driver for his father and discovers the company’s cover-up of multiple road deaths, he must expose his father’s negligence before someone else dies.

When a disgraced --- is what you're looking for, not when disgraced. I think the logline is executed well. I just think the grammar is a little bit off. I would think the logline would go like this: A disgraced banker discovers the company's cover-ups of multiple deaths and must expose his father's negligence before someone else dies.