This walkthrough covers how to get arrested. If you want to take the sneakier option and follow Iorveth’s advice, refer to the following guide. To get arrested, just approach any of the guards. The guards in the city will all be hostile towards you. They will attack you. Don’t fight back (unless of course you enjoy it) and allow your health to drop to zero. Instead of dying, you will be transported to a prison cell. If you want to have a little more fun with getting arrested, you can sneak over to the nobles playing dice at the left-hand table in the center of the city, and start beating them up. Either way, you will end up in the same cell. You will have lost all of your equipment, but you will be able to get it back soon enough.
You will find yourself in the cell right next to Philippa. She won’t know anything about your knowledge of her plan, so your sudden appearance in jail will be a big shock to her. Tell her about your knowledge of her plan, and she will defend herself. She will say that she didn’t know about Saskia being a dragon until she was poisoned. At this point, Philippa found out Saskia’s secret while magically searching for a cure. Taking stock of the situation, Philippa simply decided to make use of this new information to gain a powerful partner. After her explanation ends, (Spoiler) Shilard and Radovid will barge into Philippa’s cell and gouge her eyes out (End Spoiler.) Radovid will then inform you that he will keep you imprisoned for as long as the peace summit takes to end. Shilard will enter your cell with two guards and begin to interrogate you. A Quick Time Event will appear onscreen. Hit the left mouse button repeatedly to escape and overpower the guards.
As you leave the prison, the wounded Philippa will give you a choice; you can either help her by bringing her to her house, or help Triss by invading the Nilfgaardian camp. If you help Philippa, she will promise to remove the spell from Saskia. If you do one of these, you naturally cannot do the other. With this choice in mind, you will complete the For A Higher Cause! quest, and you will receive 500 experience points.