Arrow season 1 episod 21
Watch online episod 21 – "The Undertaking"
Oliver tracks down an accountant, Backman, for the secret organization and steals his laptop in order to redistribute all of his money back to the people he stole from. While decrypting the laptop, Felicity uncovers a link to Walter—a $2 million transfer was made to Dominic Alonzo, an underground casino owner who was hired to kidnap Walter. With Felicity posing as a card sharp, the pair infiltrate the casino; after being beaten and threatened, Alonzo reveals that Walter was killed. Oliver informs his family; Moira immediately confronts Malcolm, who reveals that Walter is alive. Oliver, who was listening in, discovers that Tommy’s father is heading the secret organization, and uses Felicity to hack into his phone records to ascertain Walter’s location. As the vigilante, Oliver frees Walter and reunites him with the family. Meanwhile, Laurel goes to Tommy to get the truth about why he left, and Tommy reveals that he believes she is meant to be with Oliver, who still loves her. In a flashback, Robert Queen is shown disagreeing with Malcolm’s proposed "Undertaking", which would involve leveling the Glades and kill thousands of people in an effort to rebuild the area and remove the crime. As a result, Malcolm has a bomb planted on the Queens’ yacht just before Robert and Oliver set off.