Case file · Series 25, Episode 1 · Season 25, Episode 1
Treasures of Darkness
A riverbank discovery intensifies a rivalry between mudlarking groups before a suspicious drowning revives an old disappearance.
Verified filming locations
Every filming site currently documented in this Casebook file is listed here. The published evidence does not establish a complete production itinerary.
- St John the Baptist Church · Little Missenden, Buckinghamshire
The church appears as the parish church of Goldworthy's unnamed neighbouring village.
Site guide → Filming source ↗ - The Red Lion · Little Missenden, Buckinghamshire
The pub is presented on screen as The Speckled Trout.
Site guide → Filming source ↗ - The Manor House · Little Missenden, Buckinghamshire
The property supplies the exterior of Alice Gideon's home.
Site guide → Filming source ↗
Map lookup by place name. A private house’s exact address is not marked.
Selected episode credits
Treasures of Darkness cast
These selected cast entries link to their published profiles. They do not include every name shown in the end credits.
Fiona Dolman
Isabel Shaw
Camilla Marie Beeput
Tony Way
Poppy Miller
Killian Coyle
Ben Jones
Adrian Rawlins
Jayde Adams
Gary Wilmot
Kate Anthony
Jude Akuwudike
Manpreet Bachu
Varpu Kronholm
Francesca Cozier
The 60-second case card
Should I watch this one?
A traditional village mystery in which objects recovered from the river disturb the stories people have told for years.
- Best for
- Mudlarking · River treasure · Old disappearance
- Mood
- Classic
- Team
- DCI John Barnaby with DS Jamie Winter
- Spoiler guidance
- Read the premise freely; open the marked sections only after watching. Check the linked provider advisory for further viewing information.
Why it matters
A traditional village mystery in which objects recovered from the river disturb the stories people have told for years.
Two rival groups arrive at the same Goldworthy riverbank in search of historic objects, and an argument over a newly found ampulla sets the tone. When Jonny Hoxham is discovered near the jetty, what first resembles an accidental drowning is revealed to involve a deliberately concealed hazard.
At the same time, Lucy Weaving returns to ask what happened to her aunt Jessica, who vanished after breaking with her family. A bicycle recovered from the water draws the present investigation towards that older absence and makes Lucy herself a target.
Break the seal: reveal the finding
Who was the killer in Treasures of Darkness? (spoiler)
The new deaths and threats are tied to Jessica's disappearance, the relationships surrounding her departure and the evidence that the river has finally returned.
More episode detailsProduction, cast, deaths and filming information
Credits, context and checked facts
Production and cast
- TV series
- Series 25
- Episode number
- Episode 1
- Written by
- Julia Gilbert
- Directed by
- Paul Gibson
- Listed transmission date(s)
- 8 December 2025
- Reported filming period
- March–April 2025
- Detective
- DCI John Barnaby
- Partner
- DS Jamie Winter
- Pathologist
- Dr Fleur Perkins · Annette Badland
- Principal setting
- Goldworthy
- Casebook tone
- Classic
Sources accompany the production credits and filming links.
Fictional settings and real filming places are listed separately. Filming links include 1 mapped area; 3 exact sites.
Credits and archive connections
- Writer credits7 episodes credited to Julia Gilbert
- Director credits3 episodes directed by Paul Gibson
- Release positionCase 141 of 144
- Story characterClassic · Mudlarking · River treasure
- Location evidence3 exact screen-use matches
The village church, Red Lion pub, manor house and Village Road supply Goldworthy locations, including the fictional Speckled Trout.
The case uses mudlarking finds and a recovered bicycle as separate physical routes into the village's past.
Sources for the production file
Published episode chronology and credits ↗Official ITV programme page ↗Filming-location reference index ↗Credits follow the linked chronology. Dates can differ between territories. Consult original credits for story, teleplay and adaptation wording. External synopses may contain spoilers.
The performers behind this case
Core cast
Follow the cast links for full actor and character guides.
Neil Dudgeon
John Barnaby · Detective Chief Inspector- Messiah
- Life of Riley
- The Mrs Bradley Mysteries
Nick Hendrix
Jamie Winter · Detective Sergeant- Black Mirror
- Marcella
- The Crown
Annette Badland
Dr Fleur Perkins · Police pathologist- Ted Lasso
- Doctor Who
- EastEnders
Image credits identify the licence used. No programme publicity stills are reproduced.
Forensic team
Dr Fleur Perkins
- Credit
- Resident pathologist
- Played by
- Annette Badland
Spoiler-controlled deaths
Deaths recorded in this case
3 people die in this case, according to the linked death record.
Break the seal: reveal the list of deaths
- Jonny Hoxham
Murder · Drowning
Performer check- Jonny Hoxham: Ben JonesThe earlier synopsis-derived list expanded the victim’s name to Jonathan Hoxham; the published cast record supports Jonny Hoxham, used here.
- Rufus Coulter
Murder · Other recorded death
Performer check- Rufus Coulter: Gary Wilmot
- Jessica Clissold
Murder · Other recorded death · historical or before the main case
Performer check- Jessica Clissold: not listed in the current published cast recordThe historical victim is named in the episode synopsis, but no Jessica Clissold performer appears in the current published cast record; Young Jessie is a different credited character, so no identity is inferred.
Break a second seal: reveal the verified killer
Who was the killer in Treasures of Darkness? (spoiler)
Alice GideonAlice killed Jessica 'Jessie' Clissold during a confrontation years earlier and hid her body, then killed Jonny Hoxham after he saw her checking the burial place and Rufus Coulter when he recovered evidence. She later tried to kill Lucy Weaving; William Gideon's confession was false and intended to protect Alice.
Verified motive
Alice's childhood abandonment made her desperate for safety and terrified of being left again. She killed Jessie during the confrontation when Jessie threatened to expose their relationship after Alice abandoned their escape plan, then killed Jonny and Rufus to keep that death and the ring hidden and attacked Lucy when her investigation threatened the life Alice had built with William.
Real place → fictional identity
Where was Treasures of Darkness filmed?
St John the Baptist Church
Used as: The church appears as the parish church of Goldworthy's unnamed neighbouring village.
Representative photograph of the real filming location; the exact camera angle or building may differ.The Red Lion
Used as: The pub is presented on screen as The Speckled Trout.
Representative photograph of the real filming location; the exact camera angle or building may differ.The Manor House
Used as: The property supplies the exterior of Alice Gideon's home.
Representative photograph of the real filming location; the exact camera angle or building may differ.Sources accompany the identified filming places.
Wider filming areas