You will do this

Whilst Allan is working for the Sheriff and Gisborne he goes through so much pain and sorrow, particularly when a visiting nobleman takes a shine to him and abuses him both Sexually and Physically. Every night he's locked in his room and he sits in the window staring at Sherwood Forest remembering all the good times he had with Robin and the others.

When Marian overhears the Sheriff agreeing to sell Allan to the abusive nobleman, she goes to tell Robin but Robin and most of the others haven't forgiven Allan for betraying them. But Will forgave him long ago and he agrees to help Marian.