In settings where there are long established underworld thief, criminal and otherwise ne'er do wells there is going to be a system of heraldry associated with those who live in and rule from the shadows.
The PC's enter a town amid a giant celebration, the Spring Wedding Festival. Unmarried men and women from all over the provinces gather her every spring to be matched by the most sacred matchmaker ever to live, Holly Lovard. Holly is now ancient and must be carried everywhere she visits and rumors are that this will be her last visit to the Wedding Festival so any matches made this spring will be doubley blessed.
Enter PC's, wrong place at the wrong time. Molly sees one of them, calls him/her out of the crowd and that are unable to resist the push and pull of the mob. Brought in front of Molly Lovard, the PC is declared the lifemate of
Could be the king's daughter, a peasant, member of the thieves guild. Could be anything to add a twist to an already building plot, or just throw the characters into an awkward situation.