伊恩麦卡勒姆(Iain McCallum)博士是最初的主角，由 John Hannah 饰演。麦卡勒姆是一位法医病理学家，他乘坐凯旋摩托车旅行，并破获了谋杀案。这个角色与其他两个主要角色乔安娜和后来的安吉拉有过浪漫的关系。最后一集没有麦卡勒姆和安吉拉，因为故事说他们在美国找到了工作。他们被 Dan Gallagher 博士和 Charley Fielding 博士取代。

McCallum is a British television series that was produced by STV Productions.

Dr Iain McCallum was the original lead character, played by John Hannah. McCallum was a forensic pathologist who traveled by Triumph Motorcycle, and solved murders. The character had romantic involvements with two of the other principal characters, Joanna, and later Angela. The last episode did not include McCallum and Angela as the story stated that they had taken jobs in America. They were replaced by Dr. Dan Gallagher and Dr. Charley Fielding.