[s1e19]: Compass

: To help Frankie process DNA samples while on the run, Mac creates a DIY centrifuge using common items like a bicycle wheel or salad spinner—noted as one of the best "hacks" in the series.

: The story reveals Mac’s past at MIT, including the fact that he was enrolled at age 17 and had a major crush on Frankie. Further Story Development [S1E19] Compass

: Frankie’s DNA research could be linked to future "Phoenix Foundation" cold case files or Mac's own family history. : To help Frankie process DNA samples while

Mac eventually discovers that Frankie is alive; she to hide from someone trying to suppress her groundbreaking scientific research—identifying DNA from cold cases. The episode follows Mac and Jack as they navigate the tunnels beneath MIT to help Frankie finish her work while evading a killer. Key Story Beats & "Hacks" Mac eventually discovers that Frankie is alive; she

: Jack breaks his arm in a trash compactor at the beginning of the episode. This occurs because Mac tells him to hold a pipe "perfectly normal" (a physics term meaning perpendicular), which Jack misunderstands.

: Mac creates an electric whip from a cut extension cord to defend the team against the gunmen pursuing Frankie.