The CW have released an official synopsis for episode 20 and 21 of ‘Arrow’ Season 4, titled “Genesis” and “Monument Point”

Episode 20 Official Synopsis:

“Genesis” — (8:00-9:00 p.m. ET) (TV-14, LV) (HDTV) 

DIGGLE IS CONSUMED WITH GUILT AND SEEKS REVENGE – As Oliver (Stephen Amell) and Felicity (Emily Bett Rickards) look for a magical solution to defeat Darhk (guest star Neal McDonough), a vengeance-driven Diggle (David Ramsey) gets a lead on Andy’s (guest star Eugene Byrd) whereabouts and heads off to confront his brother. Meanwhile, Alex (guest star Parker Young) takes Thea (Willa Holland) on a vacation that quickly turns into a nightmare. Gregory Smith directed the episode written by Oscar Balderrama & Emilio Ortega Aldrich (#420). Original airdate 5/4/2016.

Episode 21 Official Synopsis:

“Monument Point” — (8:00-9:00 p.m. ET) (TV-14, LV) (HDTV) 

TOM AMANDES RETURNS AS NOAH KUTTLER – When Team Arrow learns what Damien Darhk’s (guest star Neal McDonough) next move is Felicity (Emily Bett Rickards) realizes she needs to ask her father, Noah Kuttler (guest star Tom Amandes), for help. Noah and Oliver (Stephen Amell) have a heart to heart talk that leaves Oliver rattled. Kevin Tancharoen directed the episode written by Speed Weed & Jenny Lynn (#421). Original airdate 5/11/2016.