A homeowner answered a knock on the door only to be threatened by a man with a burn mark on his forehead who then ran way.
The bizarre incident happened at about 9pm last night in Adeyfield Gardens, Hemel Hempstead.
But when the homeowner challenged his aggressor, who had a burn mark above his left eye, the man ran off.
He got into the passenger side of a grey or silver car – possibly a BMW – that was parked nearby, and it drove off.
The man is described as white, aged around 25 to 30 years old, around 1.72m – or 5ft 8in – tall, of slim build, with fair hair. He was wearing a grey hooded top.
Detective Sergeant Laurence Rush, who is investigating what happened, said: “I want to reassure residents that incidents of this nature are very rare. Thankfully the victim was not hurt.
“I would like to appeal to anyone who thinks they may know who this man is to get in contact with me immediately.
“I would also ask anyone who has information about what happened, or who saw a similar vehicle in the area at the time of the incident, to get in touch.”
Anyone with information is asked to contact Detective Sergeant Laurence Rush via Hertfordshire Constabulary’s non-emergency number 101, quoting crime reference D1/14/5682.
Alternatively call Crimestoppers, the independent charity, anonymously on 0800 555 111.