|“||No victory without sacrifice, remember?||„|
|~ Beth reciting the True Believers' slogan to her husband on The End of the Beginning|
Beth MacLeish was the Second Lady of the United States, being the wife of former Vice President Peter MacLeish, who were both part of the conspiracy against the U.S government. Throughout the season, Beth tries to keep Peter in the running to take over the Oval Office by killing Tom Kirkman.
When her husband, Peter began to have second thoughts about going on within the conspiracy before becoming Vice President, Beth reassured him. She stood alongside him when he was sworn as Vice President.
Beth got into a confrontation with Peter over Alvin Joyner's fate. While she argued that he had to die due to the possibility that he might spill information about the mission he and Peter did in Afghanistan, Peter insisted that he would reassure him. Beth reluctantly agreed, but told that if he couldn't, he had to die and quoted the True Believers' slogan "no victory without sacrifice".
After a text from Brooke Mathison, Beth realized that FBI agent Hannah Wells was very close to connecting the dots and pinning Peter. She lied to her Secret Service, claiming she was going to read to her children. Beth then drove to Arlington Cemetery and saw Wells holding Peter at gunpoint. As a last resort to keep the conspiracy under wraps, she shot and killed Peter and then turned the gun on herself, committing suicide.
Initially, Beth seemed like a caring and civil person, as shown when she told her alibi that her kids went missing the day the Capitol exploded. Nevertheless, she uses this as a facade to cover up her true motives.
Beth's true personality mirrors that of Shakespearean character Lady Macbeth, as they both continuously convince their husbands into doing things that they deem immoral; in Beth's case, convincing Peter to aid the conspiracy. This can be seen when she reassured Peter into swearing in as Vice President despite him having seconds thoughts about continuing the conspiracy. This is also displayed when she tried to convince him that Alvin Joyner had to die in order for their tracks to be covered.
She was so devoted to the conspiracy that she prioritized it over her own life, evident when she kills Peter and herself so that they would not be caught by the FBI.