im stuck on it, i’ve interacted with almost every object and talked to all the people about the objects but i cant figure about who it is, please help

A: After speaking with everyone downstairs, you can go up and find a strange potion. After finding the potion you have to talk to Winona, Lady Redwood and then Irinlia. The order is important, since their dialog's affect each other in this order. Afterwards, Ryen can solve the crime by talking to the soldier next to the corpse of Sir Redwood. The right choices are Irinlia – poison – by mistake.