Complex sentence: Lee asks for a girl he saw earlier in Han's entourage, who he remembers from Braithwaite's briefing as Mei Ling, an agent whom Braithwaite had placed on the island to gather intelligence: however, she has been unable to escape Han's strict observation.
Split into simpler sentences: Lee asks for a girl he saw earlier in Han's entourage. However, she has been unable to escape Han's strict observation.