Detectives are hunting a man who jogged fully naked along the cycle track in Lancaster, leaving a woman badly shaken.
She was walking between Vicarage Field and Long Marsh Lane when she heard a noise, turned round and saw the nude jogger running towards her.
But before reaching the 21-year-old, the man turned and ran off towards Lancaster Castle.
It happened at around 7.45pm last Monday, April 7.
Police have released an e-fit of the suspect and urged women not to walk alone and stick to routes in busier areas.
Patrols have also been stepped up in the area in a bid to reassure residents.
Officers have not said whether they are linking the incident to another which happened on March 19, when a man wearing only green trainers grabbed a 52-year-old woman who was jogging on the track near Aldcliffe Lane.
DS Martin Foley, of Lancaster CID, said: “Understandably, this incident has left the young lady very shaken, particularly as she was walking on her own at the time.
“If anyone has any information about this man, or thinks they have witnessed or been subject to something similar, please get in touch with us.”
The man is described as in his early twenties, 5ft 10, slim, with a pale white body and short brown hair.
Anybody with any information is asked to contact Lancashire Police on 101, or Crimestoppers anonymously on 0800 555 111.