The CW isn’t pulling any punches with Season 4 of its flagship superhero TV series, “Arrow.” After being given an impossible ultimatum at the end of last week’s episode, Oliver Queen (Stephen Amell) must decide how far he’s willing to go in order to save his sister, Thea (Willa Holland).

When last we left the intrepid archer, an old friend had given him a grim proposition. After capturing her earlier this season, Nyssa al Ghul (Katrina Law) returned to get her revenge on the new leader of the League of Assassins, Malcolm Merlyn (John Barrowman). She approached the Green Arrow, who was sitting by his sister’s bedside and told him that she would give him something that could save her called the Lotus. In exchange, he will have to kill Merlyn.

According to the episode’s official TV Guide plot synopsis, this moral struggle will be the backbone of episode 13, “Sins of the Father.” Although Laurel Lance (Katie Cassidy) will attempt to convince her former mentor, Nyssa, to drop the grim ultimatum, it clearly doesn’t go well.

In a teaser trailer for the new episode, Oliver appears to have made his choice and is seen engaging Merlyn in a sword fight to the death, which isn’t exactly surprising. As previously reported, Merlyn was the main villain in Season 1 and has only stuck around thanks to a reluctant truce sparked by the revelation that Thea is actually Merlyn’s daughter. With her life hanging in the balance, the only thing preventing Oliver from stopping the villain once and for all is his moral code to never kill.

Arrow "Arrow" Season 4 introduced The Calculator (Tom Amandes, left) as the father of Felicity Smoak (Emily Bett Rickards, right). He'll continue to be involved in her life during episode 13, "Sins of the Father." Photo: the CW

While drama is unfolding between those with super-skills, the characters with computer skills have some inner turmoil of their own. During last week’s episode, Felicity (Emily Bett Rickards) learned that her father was back in town. However, what only the audience knows is that he’s also her arch nemesis, DC Comics villain The Calculator (Tom Amandes). Although she thinks of him as an annoyance and not a danger, a teaser image for the new episode (above) shows him back in Felicity’s life, likely trying to make up for not being there in the past.

Fans eager to see how all of these events finally shake out will just have to tune in to episode 13 of “Arrow” Season 4 when it airs on Wednesday at 8 p.m. EST.