A man had acid thrown in his face after he refused to buy cannabis from the attacker.
The victim, a 32-year-old man, was approached in Stratford, east London, by two men, in what is believed to have been an attempted robbery.
When he refused to purchase cannabis from the men he had a corrosive substance thrown on his face.
He ran into Stratford station looking for help from members of staff and was rushed to hospital for further treatment. He suffered serious burn injuries and permanent scarring.
No arrests have been made so far but police have released an e-fit of the suspect.
He has been described as a man in his late 20s, of Mediterranean appearance and of slim build. He was clean shaven, spoke with a London accent and wearing a bright red hooded-top, a dark-coloured baseball cap and dark trousers.
Detective Constable Suhal Miah said: "This was a horrific attempted robbery where the suspect didn't hesitate to spray his victim with a corrosive substance, knowing full well that it would likely cause life-changing injuries to his victim.
"We need to identify the man responsible, and we would urge anyone who thinks the e-fit looks familiar, or knows anything about the incident to come forward and talk to us."
Anyone with information about this robbery can call call Forest Gate CID on 0208 217 5820, or Crimestoppers on 0800 555 111 if you wish to remain anonymous.