A hacker has taken over a lab that deals with neuro-toxic material. All the hacker wants is for the President to publicly state what went wrong in the Baghdad bombing that Walter's tech played a role in.
There's already one man down, and the White House is getting antsy. The plan is to release the truth about Baghdad in a massive information dump, by releasing a lot of declassified documents at once.
Cabe has no choice but to tell Walter the truth. Three days before the bombs were dropped, Cabe found out that the plan was to use Walter's tech with bombs. He never told Walter this, and Walter does not take it well.
Walter makes a demand that after this case, Agent Callo needs to be removed from Scorpion or he will quit. Tensions are high, and Walter refuses to talk to Cabe. Paige manages to convince Walter that he needs Cabe as back up when they break into the facility.
After a narrow escape, Walter and Cabe are in the building. Walter goes to talk to Dr. Simon Boyd who is the hacker, while Cabe gets everyone out without Simon noticing. This goes sideways when Walter confesses his part in Baghdad and Simon sees Cabe.
Simon releases the gas and declares that he will kill Walter on live TV. Then there's Ralph, who just ran into the building because he is a part of Team Scorpion. He patches up the hole in the incinerator.
Miraculously, everyone makes it out physically okay. Emotionally? Not so much. Walter still demands that Cabe quits, and Cabe agrees. Paige tells Walter that she is leaving because it isn't safe for Ralph. Then, Walter goes and drives his shiny new car off a cliff.