When Ian and Julie moved into their Surrey cottage nearly 20 years ago, they discovered a curious wall painting in one of the bedrooms. They had no idea who put it there. Julie wanted to get rid of it as it didn't match her decor plans, while their four-year-old wanted to colour it in with her crayons.

Fiona Bruce and Philip Mould investigate a delicate sketch depicting a mother and child, purported to be by one of the modern art world's most famous names, Amedeo Modigliani. Its owner, Henrietta Sitwell, inherited the work and always believed it to be genuine. However, a leading auction house recently cast doubt on its authenticity. If the work is genuine, it could be worth up to £100,000. If not, just a few hundred.

Fiona Bruce, Philip Mould and the team help Americans Kim and Chuck, who believe their landscape painting is by one of the founders of Impressionism, Alfred Sisley, building a case to prove its authenticity. Kim and Chuck bought the work at auction near Chicago and believe it to be genuine. However, the painting was turned down nearly 10 years ago by the authentication committee, so the team will have to find new evidence to persuade them to change their mind.

Fiona and Philip visit a church in Port Glasgow to investigate whether a mysterious work depicting Christ after the crucifixion could be a lost masterpiece by one of the great painters of Northern Renaissance art.