Murdoch (Bisson) is an intelligent, observant detective who uses unusual (for the time) techniques such as blood testing and fingerprinting. Throughout the series it is revealed he comes from Nova Scotia and is a devout Roman Catholic. In one episode it is revealed that he believes that his father beat his mother and may have indirectly caused her death, although this was proved incorrect. Following that incident, he was taken to live in an orphanage.

Even though very logical, sceptical, observant, scientific and clear-headed with a photographic memory, these become an issue when he needs to connect with people on an emotional level, something he finds difficult. Often his unusual techniques and unbiased opinions of people lead him to clash with Brackenreid (even though they work together well).

Murdoch often consults on cases with Ogden, with whom he is infatuated, although he did not attempt a relationship with her until the first half of the second season. As the season progressed an argument over beliefs and past decisions made by Ogden split up the couple for a time, during which time Murdoch pursued a relationship with Enid Jones. However, he and Ogden rekindled their relationship during the season two finale on the advice of his half-brother (see below), and it becomes "public" (despite everyone already knowing about it) in the first episode of season 3.

In the season two finale it is revealed his father had another son, Jasper Linney (of whom Murdoch knew nothing), before marrying Murdoch's mother. Jasper is a sergeant in the North-West Mounted Police and his mannerisms, interests and investigative techniques are similar to those of Murdoch's own and the two prove successful in working together to solve a gold mining scam case