As thriller The Bay returns, a fire in moody Morecambe sees DS Townsend drowning in a sea of secrets

A devastating fire engulfs a family home, its flames leaping into the sky. A terrified woman trapped inside screams as she realises she can’t escape. This is the harrowing sight that opens the fourth series of ITV’s thriller The Bay, ensuring its reputation for gut-wrenching emotional scenes continues.

Set in Morecambe (hence the title, and the windswept seascapes), the series centres on a family liaison officer with West Lancashire Police whose job is to support the relatives of victims of serious crime. Morven Christie played DS Lisa Armstrong in the first two series, but was replaced by Marsha Thomason as DS Jenn Townsend for series three. In Jenn’s first case the body of a young boxer was discovered in Morecambe Bay, and this time she must glean information about the fire and the family whose home it destroyed.

‘At the start of episode one Jenn gets a phone call,’ says Marsha, 47. ‘She gets there as soon as she can and this house is ablaze and the kids are outside shouting. It’s heart-breaking. The fire was really intense, very harrowing, I got very emotional.’

Morven Christie played DS Lisa Armstrong in the first two series, but was replaced by Marsha Thomason as DS Jenn Townsend for series three (pictured) 

As the series progresses we start to learn as much about the family as we do about the police investigation – and it’s this combination of personal drama and criminal investigation that marks The Bay out from other shows and has seen it sold to more than 170 countries. ‘The thing about The Bay is that it’s both a crime drama and a family drama,’ says Marsha. ‘Jenn’s job comes at the worst time in a family’s life. When there’s a crime, she goes in and supports them through their grief.’

The family in this outing are the Metcalfs, headed by dad Dean (Joe Armstrong). When his wife dies in the fire and it’s deemed to be arson, Dean is faced not only with an investigation but trying to comfort his four children.

The investigation soon gets into full swing, but this series also wades into Jenn’s personal life, which is thrown into turmoil by a plotline that delivers a bit of light relief. Jenn and her partner Chris (Barry Sloane) are finally enjoying life as a blended family, with their children from previous relationships… until Chris’s ex-wife Jacqui shows up. Played by Claire Goose, Jacqui’s a disruptive presence who wants to cry on Chris’s shoulder after a break-up. Naturally Jenn doesn’t welcome the intrusion.

‘Jacqui doesn’t really see the chaos she’s causing,’ says Claire, 48. ‘She doesn’t think about anybody else. It’s quite funny – these two women are fighting over Chris, and it does get heated at times.’

For Marsha, DS Townsend is her first lead role after three decades on TV, appearing in British series such as COBRA as well as US hits like Lost and Las Vegas. She moved to LA nearly 20 years ago and lives there with her husband, British lighting technician Craig Sykes, and their daughter Tallulah, nine.

Mancunian Marsha says her role in The Bay is particularly thrilling because some scenes are filmed in Manchester. ‘My husband’s from Manchester too, and our families are still there, so it’s a real gift to come back,’ she says. ‘And in this series Jenn is a lot more confident, so she challenges her boss. She also does a couple of things off her own bat that she shouldn’t necessarily do and I love that.’

The Bay, Wednesday, 9pm, ITV1.

Marsha  said the ITV programme is ‘both a crime drama and a family drama’ ahead of its return on Wednesday