"Where do we see each other tonight?"
The question was asked on Håkan Hellström's Instagram, with an accompanying video where the artist spray-painted the text "Gla Valborg".
Many were the fans who, despite short notice, understood that it could probably be about the Azalea Park in Slottsskogen - a place mentioned in Hellström's song "Valborg".
Had to be kept short
Around 7 pm, Hellström really appeared in Azalea and played a number of songs for the hundreds who got there.
However, the gig had to be kept short, as the band did not have a permit and was allowed to end after consultation with the police on the spot.
"Thank you for tonight, cheers and happy Valborg to you!", Hellström greeted on his Instagram shortly afterwards.
See pictures from the secret gig in the clip above!