"Crucible" Official Description:

OLIVER MEETS THE CANARY — Oliver (Stephen Amell) discovers a man who goes by the name "The Mayor" (guest star Cle Bennett) is bringing illegal guns in to The Glades, so Oliver sponsors a "Cash for Guns" event to help clean up the city. Unfortunately, The Mayor crashes the event with his gang and seriously injures Sin (guest star Bex Taylor-Klaus). The Canary (Caity Lotz) is furious when she learns her friend is in the hospital and sets out for revenge. Meanwhile, Felicity (Emily Bett Rickards) stuns Oliver with a bit of information about the Canary, Donner (guest star Dylan Bruce) asks Laurel (Katie Cassidy) to dinner, and Diggle (David Ramsey) reconnects with an old friend. Eagle Egilsson directed the episode written by Andrew Kreisberg & Wendy Mericle (#204).