Bill Paterson plays Dr Douglas Monaghan
Despite appearing in Sea Of Souls for three series, actor Bill Paterson admits he's still none the wiser when it comes to explaining people's fascination with the supernatural and the paranormal.
"Has it become clearer to me over the years? No, it hasn't really," he muses.
"Clearly everybody has an awareness of some sort of metaphysical afterlife or existence, but they don't necessarily do it through the Church Of Scotland or their synagogue, or wherever, anymore. Instead, they do it through all sorts of new age experiences.
"I think part of the interest is that search for meaning and nowadays no-one's going to knock you on the head, the Spanish inquisition's not going to come out and say 'Off to the rack!' for having unorthodox views.
"Fortunately we are in a society where we are allowed to believe that these strange, mystical and psychic things are in the air, if we want to."
Bill's on-screen persona, Dr Douglas Monaghan, has always provided the voice of reason in the face of the weird and downright impossible. However, as the Glasgow-born actor reveals, this series sees a dramatic shift in beliefs as the sceptical department head is forced to reconsider his position on the paranormal.
"Monaghan's involvement with the paranormal has always been very academic up until now. He's known as a rationalist, someone who employs reason and argument to everything he encounters," says Bill.
"But in these new episodes he's confronted by a sequence of events that means he can't remain detached from what is happening. He's no longer just an academic bystander on an investigation - now he's involved and the danger it presents could permanently change his life."
An unassuming, intensely private man, Douglas Monaghan has always been focused on his career, but in the new series he's forced to face the ghosts in his own life for the very first time. In order to be able to move on, he must deal with the past he has kept secret for so long.
"We haven't known a lot about his past, until now," explains Bill. "In the opening episode you are clearly made aware that Monaghan is being reminded of his marriage, the loss of his wife and the death of his newborn child.
"There's an extremely eerie s茅ance during one investigation in which parallels with his own life start to appear and he tries to reconnect with his past. We get to see a domestic side of his life that we haven't seen before, which is very interesting to play, because we begin to see a glimpse of why Monaghan is how he is.
"My feeling is that he's aware he's grieved too much and that it's time to get on with his life," adds Bill. "You know, it was 25 years ago that his wife and child died and that's a long time in anybody's life.
"This time around he is faced with the dilemma of whether he should try and connect with the past or not. The series begins and ends with Monaghan in crisis, really."
A gifted academic and a sympathetic ear for those who seek his help, Monaghan's dedication to his work means that he can often over-focus to the point of obsession.
But according to Bill, the unit's patriarch figure needs to forget about the paranormal for a while and attempt to have some fun.
"Work is what's been fulfilling Monaghan over the years and what he definitely lacks is a soul mate.
"This series there is a little touch of that with a character called Elaine [played by Phyllis Logan] who comes into his life and you get to see another side of him. There's a little frisson there and you realise there's a lot more to Monaghan than just being a sad old git," chuckles Bill.
"I can understand Monaghan's love for his job, but I've never really been as obsessive about my own work. I've never really shared the workaholic mentality that somebody like Monaghan would probably have.
"I don't think acting has ever been my passion, but it's a very nice way of making a living. It might have looked like that was the case because I've always been so busy, but it just happened that way.
"As a grown up man of sixty-something, you do think should you not have done something more that helped people in your life? You know, become a teacher or a surgeon.
"I did actually qualify as a teacher and looking back I think that would have been a very satisfying profession to be a member of," ponders the veteran actor, who played Theo in A Midsummer Night's Dream as part of the 成人快手's recent ShakespeaRe-Told season.
Bill's very first professional appearance was with the Glasgow Citizens Theatre in a 1967 production of Brecht's Arturo Ui and with five decades of critically acclaimed work under his belt, he's showing no signs of slowing down.
Bill's next project is a big screen biopic, Amazing Grace, directed by Michael Apted which stars Ioan Gruffudd as William Wilberforce, with Bill playing Lord Dundas.
"I've had plenty to occupy myself over the years," reflects Bill. "I don't really have any unfulfilled ambitions and I'm not really the sort of person who says I want to play the big classical roles.
"I'm pretty content with what I've done. I sometimes feel a little twinge when I see a good new play that I think I would have been rather good in and wish that had come my way.
"Otherwise I'm pretty happy with my lot and if that means chasing ghosts - then so be it."