Sarah and Art follow Helena's clues to a storage locker in episode 2x05 "Ipsa Scientia Potestas Est".
Source: Orphan Black — Wikia
Alison picks up Donnie after he is released from jail in episode 4x09 "The Mitigation of Competition".
M.K. shows Sarah surveillance footage of Rachel and Ferdinand leaving the building in episode 5x02 "Clutch of Greed".
Art and Sarah pull up outside Krystal's apartment and attempt to talk Krystal through the op in episode 5x06 "Manacled Slim Wrists".
Rachel presents Kira to the Neolution board in episode 5x07 "Gag or Throttle". Ferdinand attempts to blackmail the board but finds all of the information has been deleted in episode 5x08 "Guillotines Decide". Frontenac is preparing to kill Al-Khatib when Felix and Art show up in episode 5x09 "One Fettered Slave".
Felix waits outside while Art goes to the station to find out what he can about the Neolution in episode 5x09 "One Fettered Slave".
Al-Khatib drops off the car containing Sarah disguised as Rachel for Detective Enger who drives it away followed by Art in episode 5x09 "One Fettered Slave".