I Know a Secret is a 1982 short television film based upon a short story by L.M. Montgomery. The short story, I Know a Secret, was originally published in Good Housekeeping Magazine in August 1935. The story was later re-structured by L.M. Montgomery for publication in Anne of the Ingleside (1939) as Chapter 30, in which Nan is tempted to know Dovie's secret. In 1979, the original version of I Know a Secret was republished as part of an L.M. Montgomery short story collection called The Doctor's Sweetheart and Other Stories, collected by Catherine McLay.

The film was directed by Bruce Pittman and produced by Michael MacMillan, Seaton McLean and Janice Platt. The screenplay was written by Amy Jo Cooper, who later novelized the story "Aunt Abigail's Beau," book seven of the Road to Avonlea book series, which was based on the television series Road to Avonlea. The film starred Fiona McGillivray as Jane Lawrence, Andrea Swartz as Dovie, Danny Higham as Eddie, Laurel Smyth as Jane's mother, Maureen A. Hume as Aunt Helen, and Sean McCann and "Six-Toed" Jimmy Thomas. In 1987, Fiona McGillivray would go on to play Hattie Pringle in Anne of Avonlea, in another television adaptation of L.M. Montgomery's stories.

The 25-minute-long film was produced by Atlantis Films Limited in association with the Canadian Broadcasting Corporation and with participation of the Canadian Film Development Corporation in 1982. The film aired on the CBC in Canada and on Thames Television, in the UK, in 1984. On the CBC, I Know a Secret aired as part of "Sons and Daughters,"an anthology of six adaptations that included five short stories and one long poem. All of the adaptations were produced by Atlantis Films. Don McBrearty's Boys and Girls, which aired as part of the series, starred Ian Heath and Megan Follows, who later portrayed Anne Shirley in the Sullivan Entertainment Anne of Green Gables trilogy, as Margaret and Laird. Boys and Girls was based on a short story by Alice Munro and won an Oscar.

Synopsis:
I Know a Secret is L.M. Montgomery's story of Jane Lawrence, a young girl new to a Prince Edward Island village in 1931. Jane and her mother have been taken in by her Aunt Helen after her father's death. Jane meets two other children, Dovie and Eddie, at the shore, and Dovie taunts her with the knowledge that she knows a secret about Jane. Jane speaks to her mother, asking her about secrets and expressing her wish that she knew a secret that might help her fit in. Dovie challenges Jane to a test to prove she is trustworthy. Jane must write in chalk that Jimmy Thomas has six toes on his cart. She carries the test out, but bumps his cart, and the three children have a near escape. Then Dovie tells Jane her "secret" that Jane was exchanged at birth with Ellen, "Six-toe" Jimmy Thomas's daughter. Dovie claims that her father, a doctor, delivered both babies on the same night and that the babies were mixed up. Dovie professes to have read the truth on her father's medical charts. Jane takes Dovie's words at face value at the expense of her identity. She writes a letter to her mother and leaves home to confess the truth to Ellen Thomas. On the way, she runs into Jimmy Thomas, who asks her to wait and tells her that Ellen will be home soon. Jane apologizes for writing on his cart, and tells her story without waiting for Ellen's return. A surprised Jimmy sets Jane straight about the truth and even shows her how many toes he really has to give Jane her own secret. Jane returns home as herself and embraces her mother. In the final scene, Jane plays with Eddie on the shore, and when Dovie comes along saying "I've got a secret," neither Jane nor Eddie is interested in listening. Jane tells Dovie that she already has a secret.