"John Constantine" to appear in "Arrow" Episode 4.05

"John Constantine" to appear in "Arrow" Episode 4.05 (headsup via @SuperHeroHype) and I remember I've yet to post about my viewing impressions on the short-lived series, since written yolks ago! (I'll remedy that soonsoon).

“When things take a turn for the worse with Sara (guest star Caity Lotz), Oliver calls in a favor from an old friend who deals in the mystical, John Constantine (guest star Matt Ryan).” (Episode 4.05 is titled "Haunted" / Source)