Conversation so far:
Who was held in captivity?
Richard was captured shortly before Christmas 1192 near Vienna by Leopold V, Duke of Austria.
Why was he captured?
Leopold V, Duke of Austria, who accused Richard of arranging the murder of his cousin Conrad of Montferrat.
When was he released?
On 28 March 1193 Richard was brought to Speyer and handed over to Henry VI, Holy Roman Emperor, who imprisoned him in Trifels Castle.

Question: What happened after he was imprisoned?
Self-contained rewrite: What happened after Richard I of England was imprisoned?