Fake or Fortune returns for a fifth series, beginning with one of the most challenging cases the team has ever encountered. Can art detectives Philip Mould and Fiona Bruce prove that a painting of a man in a black cravat is one of the first pictures ever painted by celebrated and controversial British artist Lucian Freud, even though Freud himself denied painting it? London-based designer Jon Turner is eager to prove that a painting he inherited from two friends is in fact an early portrait painted by Freud whilst at art school in 1939. If it's genuine, it could be worth around half a million pounds. But who is the mysterious man in the portrait - and why did Freud deny it was his work? As the team hunt for clues, they are drawn into a world of feuds, rivalries and intrigue. Can those who knew Freud best help unlock the painting's secrets?

The Fake or Fortune team have been called in to investigate a mysterious painting in Castle of Park, a grand house in Aberdeenshire now run as a bed and breakfast by Becky Wilson. The painting once belonged to Becky's late husband Neil, an art dealer, and although it was unsigned he always believed it was something special - a lost masterpiece by celebrated 19th-century French artist Paul Delaroche, whose work graces some of Britain's finest collections.

An enchanting sketch of a dancer believed to have been drawn by Auguste Rodin is at the centre of an investigation that draws the team into a recent forgery scandal that has rocked the French art establishment. Alice Thoday, a Lincolnshire resident with Belgian roots, inherited the rare watercolour from her mother and has always believed it to be part of a series of works Rodin drew of a Cambodian dance troupe which visited France in 1906. It could be worth over £100,000 if genuine - but the trouble is, Rodin is one of the world's most faked artists. The quest to prove it is the genuine article takes the team to Paris and the Musee Rodin, where they search for stylistic similarities in genuine works. The provenance trail leads to Mexico City in the 1940s, where Alice's mother was given the painting by a businessman called Jimmy Heineman. Who was he and how did he get his hands on a rare Rodin sketch? The deeper the team digs, the more worrying the evidence is about the extent to which Rodin's work has been faked by notorious forgers such as Ernst Durig, a Swiss-born sculptor who claimed to be Rodin's last pupil. The team turns to scientific analysis and a handwriting expert in a bid to get to the truth. Will the world's foremost expert believe the picture is a missing sketch by Rodin himself, or a very clever fake?

Every year, the Fake or Fortune team receive hundreds of requests for help from the owners of mysterious portraits. Everyone wants to know two things - who is it, and who painted it? The team choose three of the most promising portraits to investigate further - a child, believed to be by prized modern artist Willem de Kooning, a young lady, attributed to 18th-century society painter Philip Mercier, and a formidable-looking man, said to be by 19th-century German master Adolph von Menzel. Philip Mould takes on the de Kooning case, meeting Belgian owners Jan and Chris Starckx. Could a speculative online purchase for 450 euros be a lost work painted by de Kooning in Brussels at the very start of his career? The quest to prove it leads to Miami, Florida, where scientific analysis of a similar work has the potential to yield vital evidence. Fiona Bruce wants to know how an 18th-century portrait of a lady ended up in the flat of Richard and Jenny Williams, a retired couple in Eastbourne. Conservation work might help reveal some secrets while research into the life of the artist provides some clues about the identity of the mystery lady. The investigation into the portrait of The Old Gentleman takes an unexpected turn when the team delve into the story of owner Lance Miller's grandfather, a German industrialist who bought the painting in 1947. With Menzel's work frequently targeted by forgers, has Lance inherited a rare treasure - or something more sinister? Three pictures, three important artists - but as scientific testing and investigative research unlock long-held secrets, will every story have a happy ending?