On 20 December 1950, Stedelijk Museum Alkmaar bought four superb drawings at a sale. They were portraits of young women done by Leo Gestel (1881-1941) – at least, that is what was thought! Now it it proves that one of the drawings was by Piet Mondrian (1872-1944). How could the drawing have acquired an incorrect attribution in the forty years between when it was made and the sale? Who was the sitter? What was her relationship to Mondrian? The mysterious wanderings of an impressive drawing have now been reconstructed in an intimate exhibition and intriguing book.