If you hear a group of people gathering at your doorstep and speaking in hushed tones, make sure to peep through the window before you call the police.
It might just be Perth's guerilla carollers trespassing to spread their non-denominational brand of Christmas cheer.
Led by Awesome Arts chief executive Jenny Simpson, the Mighty Camelot choir has been preying on unsuspecting homeowners for more than a decade.
Once a member has identified a home with Christmas lights, the carollers wait until nightfall before they turn up to sing their hearts out.
"We don't park right in front of the house, we park down the street. Everybody's quite edgy and nervy as we're getting into position," Ms Simpson said.
"They have to trust me to deal with whatever happens.
"We've had people come out with thunderous looks on their faces but we've never had a bad experience. If they've got lights up, they're probably in the spirit of Christmas anyway."
On Thursday in Fremantle, they sang to families who had come to enjoy the street's spectacular lights displays.
But the previous week's performance was even more special for the choir's 35 members, who unknowingly ambushed a recently widowed woman in Mosman Park.
"She joined in with all her heart and genuinely thought we were angels sent from heaven. I cried all the way home," Ms Simpson said.
"I later discovered she's one of the wealthiest people in Australia but is so lost and alone.
"I guess she's inundated with people wanting stuff from her all the time, so it was an honour to just rock up and start warbling on her doorstep."
Ms Simpson lost her mother when she was 14 and her father when she was 25, so she knows Christmas can be a difficult time for some.