Ep 20. Underneath

Oliver and Felicity have been trapped in the Arrowcave for days, and tensions between the two are running high. Though Oliver is eager to work on a way out, Felicity is more interested in hashing out their relationship problems. In a series of flashbacks, we see the couple's relationship evolve from its early days to their current state, with both highs and lows along the way.

As they work to repair a malfunctioning computer, Oliver and Felicity confront the issues that have been plaguing their relationship. Felicity is hurt by Oliver's lies and deceit, while Oliver feels that Felicity has been pushing him away. As they discuss their problems, they begin to make progress towards reconciliation.

Meanwhile, outside the Arrowcave, the rest of Team Arrow is dealing with their own problems. Diggle, Dinah, and Curtis are tracking down a rogue drug dealer, one who has been using a new and deadly drug that is causing people to lash out in violent fits. As they follow the trail of the dealer, they realize that their investigation is leading them straight to the Arrowcave.

As the team approaches the cave, they begin to realize that something is wrong. Explosions rock the entrance as they try to find a way inside, and they quickly realize that Oliver and Felicity are trapped below. Though they manage to make contact with the couple, the situation quickly becomes dire as conditions in the cave deteriorate.

Oliver and Felicity work together to try and repair the cave's systems before they run out of air, but their progress is slow and the situation seems increasingly hopeless. As they struggle to survive, they are forced to confront the mistakes they have made in their relationship and work to find a way forward.

In the end, it is a combination of their skills, their love for each other, and their trust in their friends that allows Oliver and Felicity to escape the Arrowcave. As they emerge into the daylight, they are welcomed back by their team, who are relieved to see them safe and sound. With their relationship on the mend and their team reunited, Oliver and Felicity know that they have overcome a great challenge and that they are stronger for it.