The Alik'r Prisoner is an NPC in the game The Elder Scrolls V: Skyrim
You get sent by Saadia to get information from him about Kematu's location, in the quest In My Time of Need
He is located in the Dragonsreach dungeons. Go to the throne room, then take door downstairs to the cells.
The prisoner agrees to help you if you get him released. Talk to the guards and pay his fine, and then he will tell you the whereabouts of Kematu[1]
