SPOILER ALERT Do not read on unless you’ve seen “The Flash” Season 2 Episode 2

“The Flash” delved deeper into its comic book roots in the second episode of season two, explaining the concept of multiple earths; introducing new cop Patty Spivot (Shantel VanSanten); giving us a glimpse of Earth-2 — and an alternate version of Dr. Harrison Wells (Tom Cavanagh); freaking us out about the health of one half of Firestorm, Martin Stein (Victor Garber); letting Jay Garrick (Teddy Sears) prove his heroic credentials to Barry (Grant Gustin) and the STAR Labs team — and flirt a little with Caitlin Snow (Danielle Panabaker) in the process; and introducing Iris West’s (Candice Patton) mother, Francine (Vanessa Williams), all while paying homage to a historic issue of “The Flash,” number 123, which introduced the concept of the multiverse to DC Comics canon back in 1961.

Flash out of Water: You weren’t imagining the chemistry between Jay and Caitlin during their lab scenes in episode two, according to Sears: “There’s a connection these two have, almost an instant comfort level — that wonderful thing you don’t get with too many people in life, these two experience. They’re going to explore that a little bit.”

Crisis on Infinite Earths: Thankfully, Professor Stein was around to explain the concept of the multiverse to us in this week’s episode, and in the episode’s closing moments, we actually got a glimpse of what life is like on Earth-2, including an alternate version of Harrison Wells. “It’s such a unique opportunity to have a character that everybody fell in love with and everybody hated at the same time and try to reinvent him in a different way,” Todd Helbing says of Wells’ return. “I think that was always the plan — it was just a challenge to figure out how to do that and have it be satisfactory.”

52 Problems: In addition to infinite earths, we learned that there are currently 52 breaches in the fabric of reality scattered around Central City, which means 52 holes where Zoom could pop through and deposit a villain from another world.

Better Half: Martin Stein has been an invaluable resource in STAR Labs after Wells’ demise, but in this week’s episode, he collapsed — which Todd Helbing attributes to losing Ronnie Raymond (Robbie Amell). “With what happened to Ronnie he’s missing a side of him that he’s had for quite a while now, and that’s going to start to sneak up on him.”