Supergirl and Martian Manhunter travel to Mars to help M'gann M'orzz fight against the White Martians – and get some surprising help.

So far this season of Supergirl has focused mainly on Kara and her continuing emotional struggle in the wake of her decision to send Mon-El away in the Supergirl season 2 finale. The Supergirl season 3 premiere featured a much darker Kara, who was prioritizing her identity as the Last Daughter of Krypton over Kara Danvers. Last week's episode, 'Triggers', took a much more fear-tinged look at Kara's narrow escape from Krypton and how her own time in a Kryptonian pod affected her mental state after sticking Mon-El in a similar pod.

However, this week's episode of Supergirl, 'Far From the Tree', puts Kara's emotional arc on the back burner in favor of focusing on J'onn J'onzz and his own traumatic history on Mars. Past episodes of Supergirl have revealed that J'onn's family was killed in a prison camp on Mars while being held by White Martians, as well as depicted J'onn's escape to become a refugee on Earth. Since then, M'gann M'orzz returned to Mars and has been fighting to retake the planet from the more violent White Martians. Supergirl and Martian Manhunter travel to Mars to help M'gann M'orzz fight against the White Martians – and get some surprising help.

Related: Will Supergirl Run Out of Female DC Villains?

After J'onn received a message from M'gann in the final moments of last week's episode, he tells Alex and Kara that he's traveling to Mars to help her. Kara insists on going with him and, once there, M'gann reveals that J'onn's father is still alive - but Myr'nn (guest star Carl Lumbly) has been held prisoner by the White Martians for decades. M'gann needs J'onn's help to learn the location of H'ronmeer's staff - a weapon the White Martians mean to use to wipe out the resistance - but there's a major problem: Myr'nn believes J'onn to be a trick played by his captors.

Supergirl Far From the Tree J'onn J'onzz M'gann M'orzz

Previous episodes of Supergirl that have focused on J'onn J'onzz and his history on Mars have been some of the show's best and 'Far From the Tree' continues that trend. Now, with Supergirl and J'onn traveling to Mars, the show is able to dive even deeper not only into the history of the planet - particularly as it pertains to the Green Martians' religion and the evolution of the White Martians - this week's episode also provides further insight into J'onn's family and his personal history. The result is an emotionally compelling storyline centered around one of Supergirl's strongest characters, which also paves the way for one particularly fun action sequence.

Still, while the history of H'ronmeer provides some interesting context to the Martian culture - and adds new layers of depth beyond what fans may know from the comics - the heart of 'Far From the Tree' is undoubtedly the relationship between J'onn and Myr'nn. Though they are the final two Green Martians in existence, they've had vastly different experiences, and Myr'nn having closed himself off due to his torture at the hand of his captors provides a serious roadblock in his relationship with his son. It's a fraught dynamic, but one with which Kara is able to help given her own experience in losing Krypton. Family has always been a core theme of Supergirl, and J'onn and Myr'nn provide a different - but equally compelling - exploration of that theme.

Supergirl Far From the Tree Myr'nn Carl Lumbly

As for Kara, her own emotional arc takes the back seat to J'onn's in this episode, which actually allows the Girl of Steel more of the lightness she's been missing so far in season 3. While Kara has carried the burden of her choice about Mon-El in the first two episodes, leaving her friends and family to play supportive roles, Kara takes a turn as the supportive one in 'Far From the Tree' during her time on Mars with J'onn and Myr'nn. There's a particularly pleasant moment in the episode - at the start of the fun action sequence - that epitomizes just how amusing Supergirl can be when she's not at the center of an emotionally fraught storyline.

Of course, Supergirl will no doubt return to the forefront of the series as season 3 moves along, but the end of 'Far From the Tree' sets the stage for even more familial storylines concerning J'onn and Myr'nn. Plus, with M'gann continuing to fight with the resistance against the White Martians, it's unlikely this is the last we'll see of her - and perhaps not the last time Kara travels to Mars (J'onn does have his own spaceship, after all). Still, 'Far From the Tree' is a welcomed excursion from what has been an emotionally darker season 3, one that works to bring even more depth to Martian Manhunter's character and his history on Mars.

Next: Supergirl Season 3: Does Lena Luthor Know Kara’s Secret?

Supergirl season 3 continues with 'The Faithful' next Monday at 8pm on The CW.