During his physical recovery, Reese leaves without telling anyone, or where he is going. As such, Finch decides to ignore the Machine, which is trying to give him a new number. However, Finch can't ignore the indirect source of that next number, that source which may be more troubling to him. That number, which he will be working on with Shaw, belongs to Arthur Claypool. Shaw does not notice by Finch's reaction that he actually knows him. They are certain that Arthur is the intended target as he has a brain tumor and is not expected to live much longer. The tumor is causing his memory to go in various ways, such as not recognizing his long-term wife, Diane. What is more problematic is that Arthur is beginning to ramble. Finch and Shaw see that he is being protected by Secret Service which means that he has been working for a government agency probably on some top secret projects. Those ramblings are often about something called Samaritan, which they surmise is one of those secret projects. Finch and Shaw have to find out the nature of Arthur's work, most specifically Samaritan, and who would want to get information from him before they either kill him or he passes from the tumor. Meanwhile, Reese has headed back to a place from his past where he plans to escape from what he sees as the now meaningless work with Finch in light of Carter's death. There someone may provide him with a different view of that work. And in flashbacks Finch's youth and teenaged years and the genesis for the rationale of creating a machine with artificial intelligence are shown.