In the beginning of season 3, we learn the alternative-reality Martha with shorter hair and bangs is in this world with a very specific purpose: to help Jonas find something called “the Origin.” Halfway through the season she gets an answer as to what, exactly, the Origin is out of Adam, who had been trying to figure it out himself for 66 years. Martha’s older self sent her back in time not to stop the apocalypse but to create its seed with Jonas. When alternative-reality Martha and Jonas slept together in the fourth episode, they created it: their son. “What’s growing inside you is the bridge between both worlds,” Adam explains — it’s the beginning of the knot and also the end. Several episodes later Adam succeeds in killing this Martha, thinking he’s killed the Origin with her.