What is the fine-grained topic of the following text: Riley - who has played Kyle Slater in the BBC 1 soap since October - is currently embroiled in a dramatic storyline which sees him trying to salvage a relationship with half-sister Stacey, who is currently suffering from post-partum psychosis. Only return the topic.
Riley's dramatic storyline in the BBC 1 soap about salvaging relationship with half-sister Stacey suffering from post-partum psychosis.