A woman was confronted by a pervert performing a lewd act near a tree - as he wore a pillow case over his head with eye holes cut out.
The bizarre, twisted crime happened on the picturesque High Peak Trail, five minutes from the High Peak Junction Visitor Centre, at 12.45pm on Thursday.
According to police, the lone female - who was confronted as she walked along the trail - has been left stressed and fearful.
Officers say they 'need to locate and identify this male'.
Witnesses or anyone with information should call Derbyshire police on 101, quoting reference number 19000348421.