Midsomer Murders, Set 14

• Death & Dust
• A Picture of Innocence
• They Seek Him Here
• Death in a Chocolate Box

David Mostyn is shocked to find his mother Delyth in bed with Dr James Kirkwood, senior partner in the Midsomer Market surgery. Delyth, a beautiful divorcee, is delighted when James uses the occasion to propose to her.

Her daughter Megan, James' practice manager, is equally outraged, especially when Delyth tells her they are planning to sell up and travel the world. James also has the difficult task of telling Dorothy Hutton, his late wife's mother, who is still grieving.

James asks his partner Alan Delaney to check on Dorothy later, lending him his brand new Range Rover for the journey. But when Alan has to leave the car during a storm, a pick-up truck drives into him at speed and kills him. Barnaby and Jones dig into Alan's past and discover that James once accused him of stealing £30,000 from the practice. But it was put down to clerical error and the two doctors made up.

Delyth puts her cottage up for sale as Barnaby brings in computer expert WPC Gail Stephens to trace the missing money. The detectives realise James may have been the real target and race to the surgery just in time to see a bucket of metal bolts thrown off scaffolding, narrowly missing the doctor's head.

During a walk with the Midsomer Ramblers, Dorothy confides her suspicions about Megan's lavish lifestyle. She is also worried that Alan helped hasten her daughter's death and James killed him to stop the truth coming out. Meanwhile David points the finger at Clifford Rawnsley, a pig farmer infatuated with Delyth.

The detectives travel to Snowdonia to see Bryn Williams, Delyth's friend and co-owner with her of Marchogwr Allt, a disused slate waste pile. They also visit her ex, Huw, a once violent man who recently suffered a stroke. He tells them David also called by, asking him for £250,000 for a business venture.

On the way back, WPC Stephens phones. Computer records show Megan used the money to buy cane furniture for David's shop and he shared the proceeds by buying her a sports car. But did they kill Alan or try to kill James?

As the Midsomer Ramblers gather in Snowdonia, Jones joins the trek to protect James from potential killers while Barnaby questions David about his financial misdeeds. But something David says makes Barnaby realise James is at risk from a person they never would have suspected &ldots; just as Jones realises the doctor has disappeared from the mountain path.

Rivalry between traditional film photographers and digital camera fans in the village of Luxton Deeping reaches fever pitch at the annual photographic society exhibition when snapper Steve Bright threatens black and white film enthusiast Lionel Bell.

During the private viewing, Joyce is shocked to see a print on the wall showing Barnaby caught in a passionate embrace with another woman - Marion Bell, Lionel's wife, who left him to live in Spain.

Photographer Headley Madrigal says the image has been digitally manipulated - its two shots put together. Joyce assumes it's a criminal getting revenge, then Barnaby admits he had a brief relationship with Marion 30 years ago.

Lionel is photographing his favourite oak trees in Luxton Wood when he is strangled with the cord from his light meter. A memory card from a digital camera is found in his mouth.

Police discover Lionel shared a bottle of wine with a visitor the night before he died, but according to his diary it was DCI Barnaby. Then the detective's fingerprints are found on a wine glass at Lionel's home.

Barnaby realises someone must have taken his wine glass from the exhibition to frame him but he is taken off the investigation and replaced by irritating bureaucrat Martin Spellman, who spends most of his time planning his forthcoming wedding.

The memory card reveals glamour shots of a blonde woman. Before Jones can question Steve Bright about it, he too is strangled. This time, a roll of black and white film is found in his mouth containing more images of the mystery woman.

Behind Spellman's back, Barnaby visits Lionel's daughter Philomena, who admits her mother returned to England recently. Then Headley's son Seb invites him to his dark room at night offering information about the blonde woman. He claims Bright held sessions at his studio with glamour models, plus Lionel and other middle-aged men.

Jones finally discovers who the woman is - but her identity comes as a complete shock. Then Seb invites Spellman to his darkroom for more revelations. With the evidence mounting against him, will Barnaby be able to clear his name?

A new version of 'The Scarlet Pimpernel' is being shot in Midsomer Magna, but the atmosphere off the set rivals the battles of the film. Producer Jack Braxton and director Nick Cheyney hate each other, manor house owners Terence and Diane Charteris are broke and their marriage is on the rocks, while there's a painful history between their daughter Leonie and Cheyney.

DCI Barnaby and DS Jones get interested in events when they tail known thief George Ince to a meeting at the manor with Jed Norris, another ex-con. They are amazed to discover Norris is employed there as a security guard.

Meanwhile Joyce arrives with a group of residents from The Cedars care home who have been drafted in as cheap extras. Among them is Gwen Morrison, an old friend of Cheyney's who now runs a charity shop with Leonie.

Filming is disrupted when Raymond Clandillon, a larger-than-life gay alcoholic actor arrives, begging for a role. Cheyney casts him as an extra, much to the amusement of Neville Hayward, the brother of Gwen's late husband Ted. At one point, Raymond, Neville, Gwen and Ted were local actors known as the Four Musketeers, but after Ted died, Neville's friendship with Raymond soured.

Leonie interrupts dinner at Magna Manor to warn Cheyney to stay away from her son Josh. Diane also threatens him, as does Danny, Leonie's partner. Cheyney laughs it off but, later that night, Jed finds him beheaded by the guillotine, a film prop.

Braxton and Diane have alibis after they admit spending the night together, while Danny reveals that Josh is Cheyney's son, the result of a drunken night. And according to Neville, Raymond blames Cheyney for ruining his career, while Leonie suggests her father will stop at nothing to make money from Magna Manor.

With such a wide array of suspects to choose from, Barnaby is sure young Josh is central to the case. Then Bullard reveals Cheyney was drugged with morphine before he was beheaded.

As the complicated relationships of the Four Musketeers start to emerge, there is another beheading. But who is settling old scores and why?

Reformed criminal Ronnie Tyler prepares to leave Midsomer Holm, a tranquil village and halfway house founded by Lord Holm and detective-turned-psychotherapist Professor Gina Colby. At the heart of the village is an historic camera obscura.

New arrival Eddie Marston takes Ronnie's place, which DCI Barnaby is uneasy about. Meanwhile Gina's husband Jack, a former DS at Causton, is having trouble sleeping, haunted by the past.

Jack and Barnaby were close, but Jack can't open up to his old colleague now. He left the force under a cloud after Lord Holm was jailed for killing his unfaithful wife Maria with the handle from the camera obscura. Maria's conquests included the Friday Nighters - policemen who had sex with her in the cells while Jack was on duty.

After the scandal, Gina had resigned and retrained as a counsellor, and had visited Lord Holm in prison. When he got early release, he invited her to expand her work with offenders. Jack, now a probation officer, recommended Eddie for Midsomer Holm, even though he was the cop who got him jailed.

Cully and Simon arrive for a surprise visit, but Barnaby is called away when Jack's Land Rover is found wrecked in a ditch, with Jack dead. Bullard says Jack was murdered with a heavy iron bar.

The detectives learn that Jack was upset by financial problems at Midsomer Holm and his mood changed suddenly a month ago. Meanwhile Eddie Marston has disappeared.

Postman Lionel Poulter, one of the Friday Nighters, intercepts an envelope sent by Jack to Barnaby, containing newspaper cuttings and a threatening note. He phones Eddie but is found by Barnaby and Jones and forced to admit that he's been blackmailing Jack since meeting Eddie in jail. But what was Jack so anxious to hide?

• Biography of Caroline Graham