Plot summary
With 24 hours left before Iris dies, Team Flash makes their final preparations: Cisco Ramon and Tracy Brand learn that there is only one energy source that can power the "Speed Force Bazooka"; the salvaged Dominator battery held by A.R.G.U.S. However, director Lyla Micheals refuses to hand it over because of her mistrust of Barry Allen due to his abuse of time travel erasing her daughter from time.
Running out of options Barry travels back to 1892 Siberia and recruits Leonard Snart, when he was travelling with the Legends, to help steal the device from A.R.G.U.S. The robbery goes well and as they make it to the device only to discover it is being protected by King Shark. Barry prepares to break his "no kill rule", but Snart stops him and uses the cold gun to put him to sleep. They steal the battery, waking King Shark and triggering a lock down in the process. Snart is unable to get out in time, Barry manages to cut King Sharks arm off. Moments later, A.R.G.U.S. arrive and capture Barry and Snart, but Lyla seeing the kindness in Barry's actions allows him to take the device. Snart advises Barry to use the goodness in him to defeat Savitar.
Back at S.T.A.R. Labs, Cisco has a vision about his battle with Killer Frost and leaves to fight her. While Barry goes to return Snart, Joe West hides Iris Earth-2 with Harry Wells, but Savitar tricks H. R. Wells into revealing her location by pretending to be Barry. He travels to Earth-2 and kidnaps her. Both Barry and Savitar travel to Infantino Street and fight, Barry uses the "Speed Force Bazooka" on Savitar, but it fails when Savitar counteracts it with the Philosopher's Stone, which is made out of calcified speed force energy. Savitar then stabs Iris in the back seemingly killing her, before escaping.
Credits
Adapted from Wikipedia contributors, Infantino Street. Paragraphs and formatting adjusted; illustrations, reference markers, block quotations and non-story material omitted.