Complex sentence: Ashley's return greeted him with the news from Kirk that Casey had taken Freddie, much to the distress and shock of Ashley, who upon phoning her as requested, headed towards her flat, insisting Kirk not tell Claire what was occurring.
Split into simpler sentences: Ashley's return greeted him with the news from Kirk that Casey had taken Freddie, much to his shock and distress. Ashley phoned her as requested and headed to her flat, insisting Kirk not tell Claire what was occurring.