In the final episodes of season one of Arrow, Oliver races against time in an attempt to prevent Malcolm Merlin’s plan, with an event that they called the Undertaking, to happening.
The small group of business men, including Oliver’s father and later his mother, all had a axe to grind against the Glades. Merlin’s wife was shot while working at her clinic, Oliver’s father accidentally killed someone, and Frank Chen’s daughter was raped in the Glades. Merlin’s plan was to have an earthquake created by a machine, to level the Glades and kill anyone and everyone within the Glades.
Maura admits during a press meeting that she was apart of the Undertaking in an attempt to save as many people as possible, and that Malcolm was behind the plan.
Felicity, Diggle and Oliver attempt to find the machine to dismantle it before it is set off. Oliver brings in Detective Lance to try and find the machine, which is located where Merlin’s wife was murdered in an old subway terminal. While Lance searches for the device with the help of Felicity to dismantle it, Oliver and Diggle search for Merlin as he has the switch that could turn it off.
In the island flashbacks, Oliver prevents Fryer’s plan from happening. In the process of preventing the plans, Oliver does end up taking away any means of escape that Fryers could have offered him and Slade.
Detective Lance manages to dismantle the machine as Oliver manages to defeat Malcolm as the copycat Hood, but Malcolm admits that there were two devices placed in case someone managed to dismantle one of the devices in time. The machine that does go off damages the East side of the Glades, and Tommy Merlin is among the causalities of the earthquake after he saves Laurel.