I say "he," but who knows if it's really a he, though it probably is. But what did we learn for sure about the serial killer from what we saw last night?
Well, his height rules out Gordo, since he was just a boy - not that tall - in 1996. But are we sure the car burning took place in 1996 and not 2016? That's the assumption, because Frank almost nabbed the killer in 1996 based on recognizing the car. Conceivably, the killer could have hidden the car, then decided to burn it 20 years later, based on what the older Gordo may have gleaned from Raimy in 2016.
But that unlikely scenario becomes even more unlikely when we consider who was driving the vehicle in 1996. Certainly not young Gordo, who would've been too young to drive.
Is it possible that there's more than one serial killer, or the serial killer has an accomplice, the young Gordo? We've seen stories like this on everything from Bones to Criminal Minds. But, at this point in Frequency, it's still not possible to say.
In the meantime, we'll have to be happy with the little satisfactions of time travel - Frank trying to make sense of what seem to him to be lightning fast Internet speeds in 2016 (hey, they still seem fast to me), and the inability to send visual data through Frank and Ramy's ham radio connection across time, and how the two work around that.
Frequency continues to be both a pretty good police story and a better time travel tale, and I'm looking forward to more.
See also Frequency 1.1: Closely Spun Gem ... Frequency 1.2: All About the Changes ... Frequency 1.3: Chess Game Across Time