This episode marks guest star Michael Rowe's third appearance as Deadshot in the series, and he's causing a stir in Starling City once again after killing seven overseas, including a U.S. Ambassador. According to the CW, Oliver (Stephen Amell), Diggle (David Ramsey), and Felicity (guest star Emily Bett Rickards) learn that a sting operation planned by an organization called Advanced Research Group United Support (better known as A.R.G.U.S.) is underway to capture Floyd Lawton - alive, not dead. Diggle, who has a beef with Deadshot for killing his brother, is keeping tabs on A.R.G.U.S. alongside Oliver and Felicity and is determined to see the assassin more dead than alive (with or without their help).
Meanwhile, Laurel (Katie Cassidy) takes "drastic steps" to protect a young witness, a move which exacerbates the friction between Tommy (Colin Donnell) and Oliver that emerged in "Unfinished Business." Tommy became angry after he learned that Oliver believed he was dealing Vertigo after $10,000 suddenly went missing from their nightclub's shared bank account. However, it was revealed that Tommy used the money to bribe a building inspector from discovering Oliver's hideout, which is located in the basement of the club. A favor to a friend, but a criminal cover-up nonetheless.
It seems as though the aforementioned young witness, a little boy, appears in the CW's promo, and that A.R.G.U.S. knows his whereabouts. An educated guess says then that the man in the brown trench coat that breaks into Laurel's home is guest star J. August Richards (vampire hunter Charles Gunn from "Angel") as an agent of A.R.G.U.S. trying to apprehend the young witness.
Roy Harper (guest star Colton Haynes) also returns and tells Thea (Willa Holland) that he wants to meet the vigilante face-to-face after he saved him from getting shot by the Savior in "Salvation". Unfortunately, Harper goes about it the way he knows best, running afoul of the law in the process, and is confronted by Detective Lance (Paul Blackthorne).
This episode, as every other episode has, will feature flashbacks to the island, with Oliver recalling how Shado (guest star Celina Jade) gradually helped him gain confidence with handling a bow and enabled him to hit a target with an arrow for the first time.
Moira (Susanna Thompson) also stars while Slade Wilson (Manu Bennett), Yao Fei (Byron Mann) and Lyla Michaels (Audrey Marie Anderson), whom Diggle asked for help on finding Deadshot in the previous episode and works for A.R.G.U.S., also guest star.
You can watch "Arrow" season one episode 20 "Home Invasion" on The CW at 8 p.m., ET on April 24. Or, you can watch it online by clicking the link above.