Season 2B picks up with Ben and Maddie feeling uncertain about the mermaids' future after the deadly consequences of the attack on the oil rig. With the mermaids returning to sea, Ben and Maddie are left feeling lost without Ryn. Once Helen learns she's not the only one of her kind, she discovers theirs a dark side to her people's past.
In this mid-season premere, Ben, Maddie and the other humans deal with the fallout from the attack on the oil rig, while the mermaids reacclimate to their ocean home. Ryn comes back to land to follow through on an agreement she made with the military, despite not knowing what their ultimate goals are.