A 17-year-old boy has been stabbed in the chest in what police have called a "vicious and unprovoked attack".
A male offender, described as being in his late teens or early 20s, had demanded the teenager's mobile in East Park, Wolverhampton, on Monday evening.
The attacker, described as black and 6ft 1ins to 6ft 2ins tall, ran off empty-handed after the incident, which happened near to Stowheath Lane.
The victim was taken to hospital before being released.
The offender was wearing dark clothing with a hood.
Anyone with information about the attack, which happened at about 1955 GMT, is asked to contact Wednesfield police.