Complex sentence: However, Clark believes she's the spitting image of Joplin herself and Mary takes a look, which also strikes her like a shot through the heart as everything around her fades to black and white momentarily.
Split into simpler sentences: However, Clark believes she's the spitting image of Joplin herself and Mary takes a look. Such a glance strikes Mary like a shot through the heart as everything around her fades to black and white momentarily.