- "You know, you should be careful how you treat people, my friend. After all... What goes around, comes around."
- —Digger Harkness after killing an A.R.G.U.S. security guard with a boomerang[src]
Digger was a member of ASIS specializing in weapons and technology. During this time, Digger trained with Slade Wilson several times. During Slade and Digger's final fight, Slade's Mirakuru-enhanced strength returned, and he defeated Digger.
Eventually, Digger went rogue and started selling his services to the highest bidder, after which he was captured by A.R.G.U.S. Because of his skills he got recruited for the Suicide Squad.
Member of the Suicide Squad
Digger was once a member of the Suicide Squad. During an operation in Tanzania, the team was facing the warlord outgunned, so Lyla Michaels gave the call to kill them all. However, Digger's explosive in his neck malfunctioned and didn't kill him. After this he developed a grudge against Lyla, who had killed his team and tried to take his life.
Revenge on Lyla Michaels
Oliver Queen and Roy Harper investigated his house which was wired with explosives. An intervention team of A.R.G.U.S showed up as well. However, Digger had left moments before. He used the identity card to get access to A.R.G.U.S where he quickly killed the security guards trying to stop him. Confronting Lyla Michaels, John Diggle and a squad of agents a huge firefight erupted where he used his boomerangs to corner Lyla and Diggle. Arsenal and The Arrow showed up and fought him. He was able to hold his own and almost hit Oliver with a boomerang when it got caught by The Flash. Surprised, he detonated a smoke bomb and quickly escaped the place.
Team Arrow protected Lyla and tracked down his supplier. Expecting them to come after his supplier of boomerangs, he gave the cellphone used to contact him to a Russian mobster in a bar. He then traced the cellphone of his supplier back to the Arrowcave and sneaked in while Diggle, Barry, Roy and Oliver were gone. Confronting Lyla, he got in a firefight with her, managing to throw a boomerang into her stomach. Felicity threw an explosive at him which forced him to retreat.
Believing Lyla was dead, he planted five bombs over Starling City and planned to leave by train. Suddenly, all the passengers disappeared in a blur and Arrow and The Flash were confronting him. He told them about the bombs and then activated them hoping he could escape. However, Arrow fought him while the Flash and Team Arrow dealt with the bombs. After a fierce fight he got ultimately beat and pinned to the wall by arrows. He mocked Arrow and told him he would never tell him how to disarm the bombs. Disappointed, he realized the bombs had been disarmed already. He then mocked Arrow, stating that his refusal to kill him makes him weak. Oliver retorts that it means he still has some humanity left. As Arrow turned his back, Digger reached for a boomerang, but Arrow shot him through the hand. He was later imprisoned in the A.R.G.U.S. supermax on Lian Yu.
Joining Prometheus' team and apparent death
After several months of being held prisoner in the A.R.G.U.S. supermax on Lian Yu, he was released by Oliver Queen along with Slade Wilson to help him rescue his loved ones and to stop Adrian Chase. After being released, Oliver, Slade and Digger went and met with Malcolm Merlyn and Nyssa al Ghul in order to discuss their plan. Digger and Nyssa began to have a disagreement and they all begin to bicker until the plane which Oliver arrived on is destroyed by an RPG. While Malcolm and Nyssa go to find the person who fired the RPG, Digger, Slade and Oliver continue onward to find the kidnapped members of team arrow. As they're continuing to walk along a path, Digger asks Oliver why he can't have a gun and Oliver replies because he doesn't trust him. Eventually, they come upon Curtis, Thea, Felicity and Samantha who are inside cages and as they attempt to get them out, they're ambushed by Talia Al Ghul and Evelyn Sharp. Suddenly, Digger pulls out a pistol, revealing he was working for Chase all along. He invites Slade to join, which he accepts as Oliver is forced to lower his weapon. However, Slade reveals he's still loyal to Oliver and berates Digger for trusting Chase based solely on an assumption, and him and Digger begin to fight. As the fight continued, Malcolm and Nyssa arrive, causing Talia throws down a smoke bomb which allows both her and Digger to escape, leaving Evelyn behind. While Oliver goes after Chase and the rest of team arrow, Felicity and the others go to escape. However, Thea steps on a land mine and they're unable to disarm it. Malcolm pushes her off of it and takes her place as Digger throws a boomerang into a tree, forcing the rest of the group to retreat. Digger walks up to Malcolm and wonders aloud why he's standing in the open. Malcolm replies with a smirk, "Let me show you" as he steps off the mine, presumably killing Harkness, a number of Talia al Ghul's men and, himself.
Bound on revenge, Digger is highly motivated to kill her and talked about the boomerang as a metaphor that everything comes back at you sooner or later. He is convinced that the end justified the means and even planted bombs in the city and risked the lives of countless people to escape. He mocked Oliver for his humanity and said he did not have what it takes to stop extreme people like him.
Digger is one of the few foes to ever tactically outsmart Oliver Queen.
- Peak of human physical condition: As former member of both ASIS and Task Force X, Digger is a very powerful and highly trained fighter. He easily defeated several A.R.G.U.S guards and faced the Arrow, Arsenal and the Diggle family without fear, battling the first duo and knocking Roy down.
- Master boomerang thrower: Digger is a master at throwing his edged boomerangs and is able to hit moving targets with incredible precision. During firefights and combat he uses the ability of the boomerang to fly back to throw it over the cover of his opponent and then strike them in the back.
- Master hand-to-hand combatant/Martial artist: Digger is a master hand-to-hand combatant. Using his edged boomerangs as close quarter weapons he was able to cut down multiple armed guards in mere seconds. He was even able to fight both Arsenal and the Arrow simultaneously knocking Roy down and almost hitting Oliver. He proved to be no match for Deathstroke without Mirakuru.
- High-level intellect/Master tactician: Digger is a great tactician. He was able to use his knowledge of A.R.G.U.S to break in and almost kill Lyla. He was able to lure Team Arrow away from the Arrowcave to get close to an unprotected Lyla. He used bombs in an effort to get away from Star City. Digger was ever able to tactically outsmart Oliver; a genius and master tactician in his own right.
- Explosives expert: Digger is highly skilled with explosives.
- Expert technology user: Digger was able to track the Arrowcave using the signal from mobile phone that he left to Klaus Markos.
- Boomerangs: Digger used edged boomerangs to take out his targets. In close combat he used them like cutting weapons. He also has boomerangs that are made to explode on impact from C4 in specialized grooves, acting like grenades.
- Smoke bombs: Digger used a smoke bomb to quickly escape.
- Bombs: Digger used bombs to wire his apartment and planted five of them in Starling City.
- "Lian Yu"
The Flash: Season Zero
- "Fish Fry"
- "Blood Loss"
- "A Little Help From Some Friends"
- "The Impossible Mission"
- "A Minor Setback"
- "A New Home"
Behind the scenes
- In the DC comics, "Digger" is simply a nickname for Captain Boomerang, his real name being George Harkness. In the Arrowverse, no other name but "Digger" is given so far.
- Equally, in the DC comics, Digger is often a somewhat buffoonish figure, whereas in the Arrowverse, he is a clear and deadly threat to the Arrow and the Flash alike.
- In DC comics Captain Boomerang is a villain of the Flash, even joining the Rogues. On the show however, he is more of an enemy of the Arrow. This is because Arrow has featured the Suicide Squad (a team of death row supervillains who carry out black-ops missions in exchange for commuted prison sentences) more predominately, and that Boomerang was an original member of.