Memories of Holdenshire: A Different Start
Starting off a game with everyone forgetting who they are may not be an attractive prospect for all groups. Alternatively, the party may begin as burgeoning adventurers that seek out Annika Crestveil in search of advice or guidance, learning from her brother Tariq that she was last seen entering the catacombs under the city— but he warns not to delve under Northminster and that it is a matter for the guard.
The PCs arrive to find the dazed cultists, but spotters working for the local thieves' guild see them descending below and use the opportunity to frame them (so the adventure proceeds mostly normally).
As soon as the adventurers are topside again they hear that they're wanted for conspiracy with the cult as well as tampering with criminal evidence and several other charges that numerous (bribed and lying) witnesses corroborate. Left with few other options the party returns to the cult's hideout where they discover that everything of value has been taken away, but there are several obscure markings that were not there before (which any rogue recognizes as thieves' cant with the clear message to "leave it be").
Conveniently there's also a message of gratitude intended for the decoys that helped the thieves' guild pilfer the area, urging them to contact Belton Freedew for help (if none of the PCs know thieves' cant, this can instead be communicated with a simple paper note written in Common which disintegrates when touched). Once they've traveled to a safe place with Belton (the Weirwood in Holdenshire) and earned his trust, he promises to clear their names back in Northminster—though he never makes it back.