Unbeknownst to fans of The Flash, the source of the series' season 3 villains was seen two weeks ago in the premiere.
Season one's villains were metahumans created by the explosion at STAR Labs' particle accelerator. In season 2, it was carryover from Earth-2 and the Flashpoint timeline.
In season 3? Well, when Barry Allen was making his way back from the Speed Force, he ran over a city bus and through traffic. Apparently, that bus was bathed in dark matter spilling out of the Speed Force and giving everyone on board metahuman abilities.
At the start of the episode, Becky "Hazard" Sharpe gets onto the bus, and the first visual clue we get that something is amiss is that she briefly makes eye contact with last week's villain, Kilg%re.
The Flash airs at 8 p.m. ET/PT on Tuesdays on The CW.