Complex sentence: Eve Myles previously appeared in the 2005 "Doctor Who" episode "The Unquiet Dead" as Gwyneth, a 19th century clairvoyant, with a connection to the Cardiff Rift, which later became a central plot device in "Torchwood".
Split into simpler sentences: Eve Myles previously appeared in the 2005 "Doctor Who" episode "The Unquiet Dead" as Gwyneth, a 19th century clairvoyant. Gwyneth had a connection to the Cardiff Rift, which later became a central plot device in "Torchwood".