Supergirl comes face-to-face with Cyborg Superman when she attempts to save Mon-El from Cadmus.
The Guardian debuts to lend a hand after a parasite alien drains Supergirl of her power. Mon-El considers a less than desirable new career which then leads him to contemplate his motives. Alex struggles with a new reality.
Supergirl must beat a ruthless new gang who has been armed with dangerous new alien technology. When Cadmus sends a video to the DEO, the team realizes Cadmus is the one staffing the criminals for a secret mission. Meanwhile, Kara gets Mon-El a job as an intern at CatCo, James makes an important decision and Lena invites Kara to attend one her fundraisers.
Supergirl tries to stop an alien fight club run by Roulette, while Hank gets to know M’Gann.
Supergirl and the DEO are assigned to protect the President when an attack on her causes alien vs. human rights in National City to heat up. Alex investigates the case with Maggie Sawyer while Kara fears Mon-El may be responsible.
CADMUS attacks National City with a kryptonite powered villain who ends up seriously hurting Supergirl. Superman blames Hank because the kryptonite was stolen from the DEO. Meanwhile, Kara’s first day at her new job doesn’t go as planned after she meets her new boss, Snapper Carr.