This quest opens when you read an incriminating letter that you received at the end of the Quelling the Rebellion quest.
The first thing you need to do is head to the jail cells at the Militia House in West Freeport. You will get an update stating that the froglok was moved deeper into the dungeons. Click on the door at 132, -26, 141 to enter A Musty Dungeon. This is an instanced zone available only to those on this step of the quest (mercenaries will also zone in with you).
Kill the guards, then the jailors. After this ignite the clickable barrel to blow the jail door. The froglok will flee. You can shut the jail cell to trap him and kill him, but it is not necessary. If you are doing this as a group, everyone should that needs the update should ensure that they hit the froglok. After this the quest will auto-complete and you receive a Froglok Pondstone as a reward.
Head to the Dog Pond in Commonlands and use the Froglok Pondstone. This will teleport you to The Hidden Village of Kugup. Once inside of Kugup you must complete all eight of the quests, stemmed from Uncovering the Froglok Secret, from the villagers here to gain the trust of Chief Kraol.
The note which Kath carried on her person told of a continued and determined effort to free Geraufl from the prison. It may be time to simply eliminate the froglok, rather than allow it to continue to fester and bring the simpering Qeynosians over in droves.
Geraufl must be killed before his existence invites anymore Qeynosian slime to attempt his rescue.
Find the old froglok in the jail.
It seems that the frog has been moved.
It appears that the guards have moved Geraufl deeper into the prison. Just my luck.
I'll need to slip down into the deeper reaches of the jail to kill Geraufl.
Slink down into the jail and kill Geraufl.
I've failed in my mission to kill the frog.
Geraufl has escaped through my own incompetence. Fortunately no one is left to tell the tale of my... indiscretion.
My intentions were good, but I unfortunately failed in my mission to kill the froglok. He escaped the jail while I was stunned, likely fled into the sewers. Unfortunately, I suppose this may mean we'll start to see more of them in the future.