Supergirl, “City of Lost Children:” This week features alien refugees, problematic portals, and another direction for James Olsen.

The episode also teases the possible existence of Batman in Supergirl’s universe (indirectly referenced at least once before), which keeps very much with DC history. In their early comics, Batman and Superman crossed over, but rarely interacted with other superheroes, who, in turn, often interacted with each other. The CW’s two superhero TV-verses seem to function in much the same way.

The Flash, “Cause and Effect”: Barry is beside himself over recent developments, but the Team has a plan, the dangers of which initially get played for laughs. Indeed, at one point, the episode seems to acknowledge the desirability of having a lighter, non-mopey Barry. Alas, that won’t happen just yet.

The episode reveals that Killer Frost has her own motives, though it does not reveal what they might be, and includes dazzling if artificial visual effects.

The conclusion gives us a weapon that could take down Savitar—but there’s a glitch not even Doc Brown could solve.

Arrow, “Honor Thy Fathers:” This familiarly-titled episode brings Ollie back to the mayor’s office, criminals back to Star City, and a mystery corpse to the mix.