Video report by ITV News Correspondent Rupert Evelyn
It’s the burning question that so far remains unanswered.
The police do not know where the deadly bottle of Novichok was found and Charlie Rowley cannot remember.
There are details in his account of the days before being struck with a nerve agent that are clear and on a tour of Salisbury with ITV News he has been able to rule out certain locations while keeping the door open to one possibility.
"It’s a possibility that I may have found it here." he tells us at some bins outside the back of some shops in the centre, but he says "I don’t know, all I can say is a vague description of an area and this being one of them"
Charlie had a habit of searching for "treasure" in bins. The items that would catch his attention were the new still sealed products.
He cannot be sure but thinks the most likely option is that he found it in a city bin a couple of days before he and his partner Dawn Sturgess were contaminated with the chemical weapon.
Charlie says he’s shared this same information with the police and he’s keen to help the investigation.
"It’s very frustrating… I’d like to be able to say exactly where I got it from but I can’t…. I’d love to be able to help as much as I can but it’s not helping if I make it up," he said.
We took Charlie to other key locations in the city and he was able to rule them out.
The Maltings park where Sergei Skripal and his daughter Yulia were found poisoned on the bench is an area he knows but is convinced he didn’t find anything there.
"I feel confident in myself to say it wasn’t picked up in the park…. I can safely say you can rule that out of being a danger zone," he says, referring to Queen Elizabeth Gardens which has been sealed off for weeks and is due to reopen soon.
None of the friends he was with that day recall him finding anything like perfume.
John Baker House where his partner Dawn lived is ruled out and so too is his home in Amesbury.
It is a mystery that needs resolving both for public safety and the murder investigation but for now the questions are being asked and no one is any closer to finding an answer.