IF you haven't watched last Tuesday's episode of River City, then look away now. Spoilers lie this way. Still here? Well, you have been warned …

It's a wintry February morning in Glasgow and over coffee Kathryn Howden is discussing the heart-wrenching storyline that has seen her TV soap character Maggie McLean reveal she had been a victim of rape and incest.

Viewers saw Maggie confess the dark secret to daughter Caitlin, who learns on her wedding day that the man she thought was her uncle is in fact her biological father.

Howden, 56, approached the role with considered care. "I felt a huge responsibility," she says. "Particularly if people have been through that same kind of thing. As an actor you want to do it as truthfully as possible. I was trying to think how I would feel if it was me."

Not least imagining the burden of keeping the truth hidden for all those years. "Maggie hadn't told anyone," says Howden. "He is her brother and that, I think, is the most difficult thing. It is family and that must be awful on so many levels."

While the scenes were being shot, Howden was dealing with personal tragedy in her own life. Her mother, Freda, was gravely ill and passed away in early November. The Edinburgh-born actor channelled that grief into her onscreen performance.

"I was rawer than I would normally have been," she reflects. "It helped with the emotions always being there and what I did was focus it in on the storyline."

River City fans will witness the aftershocks continue to reverberate through Shieldinch in the latest instalment tomorrow evening. "I don't think that you can expect everything to go back to being happy families again," says Howden. "It is going to take a long time."

It marks new territory for Howden who has spent much of her career in theatre. Her impressive body of work includes a three-year stint in Sue Glover's Bondagers, a powerful play about 19th-century female agricultural labourers in the Borders, which toured worldwide in the mid-1990s.

Other highlights include Howard Barker's Victory at the Royal Lyceum Theatre in Edinburgh which, directed by the late Kenny Ireland, saw Howden nominated for a national Best Actress award alongside Diana Quick and Amanda Donohoe in 2002.

There have been roles in Dominic Hill's The Last Witch and Footfalls among others. Howden is well-known to theatre audiences across Scotland from the Traverse to the Tron.

A self-described "shy middle child of three", Howden was born in Leith and grew up in the Pennywell area of Edinburgh. "My mum was delighted because we had a toilet, underfloor heating and two bedrooms after living in a room and kitchen in Leith," she says.

Her late parents Alex and Freda were childhood sweethearts. "My dad was an amazing man – and my mum was amazing to take him on," she smiles. "They met when they were 13 and got married at 18. They were madly in love – soulmates – and together for 60 years."

Joy lights up her face as she recounts an unconventional and often quirky upbringing. "We thought our childhood was absolutely normal, but it was actually quite mad," says Howden. "Whenever people asked: 'Are you working class?' I never used to know what to say. My dad didn't work 9-5."

Her father Alex "Happy" Howden, as he was nicknamed, was a colourful character and regular on the stand-up circuit. After leaving school at 15, he had variously worked as a miner, scaffolder, whaler and bus driver while trying to break into comedy.

He had a different outfit for every day of the week. "This was the 1970s," she says. "My dad would wear platform shoes and put his hair – which was as long as mine then – in rollers. My sister and I sometimes used to hide behind cars when we heard him coming."

The tales of his antics are unbounded. While working as a bus driver he was known to stop mid-route, leaving the passengers on board, to squeeze in a 20-minute open mic slot at the local social club. "He would say: 'Just nipping into the loo, ladies …'" chuckles Howden.

"He stole a bus once as well. My dad used to have a key for the depot. He couldn't get a taxi after a gig, so he just went in and took a bus. We woke up in the morning and parked in the wee tiny scheme where we lived was this double-decker bus."

Thankfully the depot manager saw the funny side. "The guy came down and said: 'Alex, can I get the keys for my bus back?' People let him away with murder. He was larger than life."

Her mother looked after the family while holding down three cleaning jobs. "My mum was a wee, strong woman," says Howden. "She was 4ft 10in and the strength of the family."

Later in life, her father landed a slew of acting roles including a memorable turn in the film adaptation of Irvine Welsh's The Acid House and playing a hangman in Martin Scorsese's Gangs of New York with Leonardo DiCaprio and Daniel Day-Lewis.

A love of performing is clearly in the genes. Howden and her elder brother Lewis both cut their teeth at Edinburgh Youth Theatre before going on to study at the Royal Scottish Academy of Music and Drama, now the Royal Conservatoire of Scotland, in Glasgow.

While filming the BBC drama Looking After Jo Jo – a gangland thriller set in 1980s Edinburgh with Robert Carlyle in the eponymous role – Howden met and fell in love with fellow actor Gilly Gilchrist. That was 1997. The couple have been together ever since.

It wasn't only their budding romance that made the shoot memorable. "I got my jaw broken on that job," says Howden. "It happened during a fight sequence with Mike Nardone that went wrong."

According to Howden, she and Nardone did a clean first take of the scene where their characters had a violent, drug-fuelled argument, but as the cameras started rolling for a second take, things went badly awry. As they grappled, a fist connected, leaving Howden reeling and disorientated.

"I think I conked out," she says. "It was the weirdest thing. Bobby Carlyle was sitting there – I knew Bobby from college because we shared a flat – and I remember him asking: 'Are you OK?'"

Howden recalls the words sounding distant and distorted. "I must have been completely out of it because I didn't feel any pain, but I could hear the cracking of my jaw."

The cast and crew, unaware that Howden was injured, began setting up for another take. "I should have said something," she says. "They went for a third time and that is what did it. My jaw had been broken but it [ended up] smashed."

Howden recounts the story with breezy good humour and is quick to stress she harbours no ill feeling. "It really wasn't his fault," she says, adding that her co-star Nardone was "traumatised" when he realised what had happened.

She returned to complete the shoot a week later, performing in two theatre shows around the same time. "I would have made a good ventriloquist," says Howden, mimicking herself talking without moving her fractured jaw.

"That was the start of my love story with Gilly," she adds, laughing. "He was brilliant and really looked after me. It was a bizarre time. I ate everything through a straw for about six weeks."

She isn't too shabby at the big romantic gestures herself. After filming wrapped on Looking After Jo Jo, Gilchrist returned to London to find his flat window had been broken and pigeon feathers – and one imagines other bird-related unmentionables – strewn everywhere.

Howden, having only newly passed her driving test, jumped in her car and drove through the night. They packed up his belongings and headed back up the motorway to Glasgow, where the couple still live today with their 13-year-old daughter Holly.

The universe has its grand plan and it was perhaps serendipity they would end up together. Howden and Gilchrist grew up just a stone's throw away from each other in Pennywell and Pilton – and unbeknownst to the pair until many years later had even lived in the same Leith street as babies.

While Howden regularly treads the boards in theatre, Gilchrist can be found gracing our TV screens in dramas such as The Replacement, Rillington Place and In Plain Sight.

"He has just finished on Outlaw King," says Howden. "Oh, I did a wee day on that too – my day with Chris Pine. It was the very first day of filming and the whole day was just Chris Pine and me. Unfortunately, I was this woman from the woods, looking manky ..."

What was Pine like? There's a twinkle in her eye. "He was lovely." The David Mackenzie-directed film about Robert the Bruce is scheduled for release on Netflix this autumn.

When it comes to future ambitions, Howden quite fancies trying her hand at directing. There is a long list of stage roles she is keen to tackle, but for the time being is looking forward to seeing where her adventures on River City will lead.

She professes to enjoying being part of the BBC Scotland series which she joined in late 2016. Howden has forged a close bond with Gayle Telfer-Stevens and Leah MacRae who play her on-screen daughters Caitlin and Ellie.

"Och, it's amazing," she says. "When I came in to the show, I wasn't sure what it would be like. It's that thing where you go into anything new and think: 'Is it going to be cliquey? Will I feel like an outsider?' But from the first day it felt like family."

River City is on BBC One, tomorrow, 8pm. Thanks to Clockwise, Savoy Tower, 77 Renfrew Street, Glasgow (workclockwise.co.uk)