Brambly Hedge - The Secret Staircase (1998)

It’s the day of the Midwinter celebrations in Brambly Hedge and Primrose and Wilfred need to recite their poem for the celebration tonight. They decide to try and practice their poem in the attic, However, Wilfred manages to find a mysterious door behind a curtain, which leads up to a secret staircase... What could be up there?