CC Jitters is attacked again after just reopening. Cisco vents to Frost about the changes that have occurred post-crisis, and the stress of the merging worlds. Nash still hangs around the lab and feels compelled to make amends for his actions that caused the crisis.
Diggle comes to visit Barry and Iris bearing a gift. Oliver has left Barry his original mask, and Barry finds Mirakuru residue on it that connects to the island Oliver had been stranded on. Barry sees this as a clue and goes on a mission to find the rest of the serum.
Iris dives deeper into her case for the Central Citizen and talks to a key witness. The source informs her there is a group in Central City called the Black Hole, recruiting and controlling meta-humans.
The source warns Iris of the danger, which later Cecile confirms. Iris becomes a target for the mercenary group as they try to cover their tracks.
The mercenary attacks Iris at the Citizen after she publishes the article. The team scrambles to Star Labs to get help. Cisco and Nash have an argument in which Cisco vents his anger towards Nash.
Iris meets up with her source, and Black Hole kills him. Iris has to speed away from the scene, but not before sustaining an injury.
The was no Mirakuru left on the island and Barry has to come to terms with Oliver being gone.