Supergirl Season 4: 5 Ups & 0 Downs From 'Call To Action'

4. The Heart Of The Matter

The Season 3 finale of Supergirl saw Lena Luthor return all of the unstable Harun-El to Alura only to reveal that she actually kept some of it. Moments before the episode concluded, Lena and Eve Teschmacher began experimenting on the rock, and that was the last we heard about it... until now.

After months of uncertainty, this week's episode revived the narrative in a rather significant way. Desperate to make a breakthrough, Lena began using the Harun-El on heart tumours in an attempt to shrink them. Although unsuccessful at first, she soon achieved unprecedented results as the heart itself became invincible.

The writers then cleverly tied this to Lena's concerns about the alien debate going on around her, as she teased the idea of potentially gifting humans with super-powers. Could the Harun-El be responsible for this? Leave it up to Ms. Luthor to find out. However, this comes at a possible cost - human experimentation.

Much like the writers have successfully done on many occasions, they are utilising the Harun-El to highlight that, although Lena has good intentions, her methods are once again flawed - and this could ultimately be her undoing.