The fifth episode of Season 1 of "Butterfly" kicks off with Rebecca and David in stealth mode, keeping a close watch on Oliver and Juno's abode. As Juno lovingly prepares breakfast for Oliver, she probes into the recent events and David's unexpected act of freeing him. Her keen instincts detect Oliver's fabrication, prompting her to urge him to cease his deceit. Eventually, Oliver caves in and reveals to Juno the exact tale he had unfurled to David. Juno, though wounded, vows to unravel the complex web and invites Oliver to accompany her to Caddis for a detailed briefing.
Once Oliver and Juno depart for Caddis, Rebecca and David seize the opportunity to infiltrate their home, subtly planting surveillance gadgets to fuel Oliver's suspicions towards his mother.
Post his rigorous debriefing session, where he was grilled relentlessly about his encounter with Dawson, Oliver returns to a house that now feels eerily different. His instincts kick into high gear as he discovers the surveillance equipment, his suspicion towards his mother escalating into full-blown paranoia.
Elsewhere, David orchestrates a meet with Dawson, instructing him to lay a trap to smoke out Juno's mole within his team. Dawson complies, drafting a misleading internal memo hinting at a high-level informant in the Karpov murder investigation. He distributes this memo, and sure enough, the mole takes the bait. She hastily contacts Juno, and they arrange a clandestine meeting to dissect the memo's implications. Unbeknownst to them, Dawson tails them discreetly, snapping incriminating photos and alerting David that his strategy has borne fruit.
Meanwhile, Juno presumes that the high-ranking witness is none other than her own son. Returning to Caddis, she learns that David has ventured to Seoul, prompting her to issue yet another assassination order. She subsequently dials her ex-partner, and they deliberate on what is best for Oliver. Her ex-partner reveals that Oliver has long yearned for his mother's approval, yet she consistently made him feel inadequate. Juno pays Oliver an unannounced visit, urgently urging him to flee Seoul at once.
Across town, David and Rebecca forge a bond while cooking and fashioning a makeshift bomb. Eun-ju calls to inquire about their wellbeing, mentioning Min-hee's troubled sleep. David reassures her that their ordeal will soon come to an end. Unbeknownst to him, Gun is stealthily approaching them.
At Oliver's residence, Juno repeats her urgent plea for him to leave Seoul immediately. Paranoia grips Oliver, causing him to storm out in a fit of anger. Meanwhile, David and Rebecca disable Oliver's guards, orchestrating a scenario that makes it appear as if his mother is having him followed. Their goal is to convince Oliver that Juno seeks his demise. To this end, they plant a bomb in his car, detonating it after he exits. Witnessing his near-fatal encounter, Oliver seeks out Dawson and agrees to testify against his mother.
After securing Oliver as a key witness, Dawson contacts David to update him. He mentions that Oliver has shared much about Rebecca, but David reminds him of their immunity agreement. With the situation improving, David suggests they celebrate their progress. They indulge in drinks, and Rebecca confesses her sense of loss. She is hesitant to abandon her career and start anew. As their conversation unfolds, Juno's men covertly infiltrate the building.
David and Rebecca part ways, promising to meet by the river. However, just as David nears the rendezvous point, Gun arrives and abducts Rebecca.
