The police investigate the headless body of Lewis Snart's technical guy in episode 2x03 “Family of Rogues”.
Jesse tracks Savitar to an empty lot and manages to wound him in the ensuing battle in episode 3x16 “Into the Speed Force”.
The gang all meets in an empty lot and are greeted by Rip Hunter with his time ship in pilot episode “Pilot, Part 1”. The heroes gather to face off against the Anti-Monitor and his shadow army to give the nerd crew time to create their shrinking device in episode 5x01 “Crisis on Infinite Earths: Part Five”.
Ryan and Alice follow Mary's receipts and discover another living victim in episode 3x06 “How Does Your Garden Grow?”.