Complex sentence: Afterwards, Mary's images were captured by the protagonists as she walked through the woods in Hush, Hush, Sweet Liars; however, they did not know of her existence and imagined Jessica DiLaurentis instead.
Split into simpler sentences: Afterwards, Mary's images were captured by the protagonists as she walked through the woods in "Hush, Hush, Sweet Liars". However, they did not know of her existence and imagined Jessica DiLaurentis instead.