Meet ‘O’ from ‘Sex Education’ Season 4: The Mystery Character Explained

By Lori Meek
Published: September 22, 2023 (Last updated: last month)
View all
Who is O in Sex Education Season 4
O and Otis in Sex Education Season 4 (Credit - Netflix)


After Moordale secondary got shut down at the end of Sex Education season 3, Otis tries setting up his sex counseling clinic at his new school, Cavendish College. To his (and the viewer’s) surprise, Cavendish already has a resident student sex therapist. Her name is O, and she becomes Otis’s nemesis. 

Who is O in Sex Education Season 4, and why is the character important?

O (given name, Sarah) first moved to Moordale from Ireland when she was in primary school. On a school-led camping trip, she met and befriended Ruby (Mimi Keene), who was ruthlessly bullied by her peers at the time.

Why does Ruby want revenge on O?

One night, O woke up to find Ruby trying to clean up after she had wet the bed. Ruby begged her new friend to stay quiet. But O cruelly told everyone about the incident, making Ruby a target for the rest of her primary school career.

At the time, O was struggling with her sexual identity and used Ruby’s embarrassing moment to make friends with the popular girls and distract the rest of the kids from her otherness. 

Why are O and Otis rivals?

When we first meet O, she’s Cavendish’s trusted and beloved student sex therapist. Otis accuses her of copying his idea and tries everything in his power to take over as the school’s sex therapist.

Otis convinces himself that O somehow stole his idea for the clinic. So he starts poaching her clients by sneakily solving the relationship issues between popular kids Abbi and Roman. He finds an unlike ally in his ex-girlfriend, Ruby, who wants revenge on O for what she did when they were in primary school together. 

Eventually, the two agree to hold an election and have the student body decide who they want to receive sex advice from. While trying to garner votes, Otis and O embark on a smear campaign against one another. In a ruthless move, O gets a job co-hosting the podcast with Otis’s mother. Yet she loses that position when Ruby releases the video of O bullying her. 

O (Played by Thaddea Graham) in Sex Education Season 4 (Credit – Netflix)

What happens to O at the end of season 4?

In the end, neither wins the election. The student who won doesn’t want the job, while Otis has the epiphany that it was wrong of him to try taking the clinic away from O in the first place, so she gets her original position back.

It also takes O most of the season to acknowledge what she did to Ruby, but when she does apologize, Ruby accepts, and the two girls finish the show on somewhat neutral territory. 

However, she does offer Otis the opportunity to work together. By the end of the series, the two seem to have become friends. 

Who plays O?

Northern Irish actress Thaddea Graham joined the Sex Education cast in Season 4 as Otis’s competition for the role of student sex therapist, O.

Thaddea Graham has appeared in several high-profile television series since her 2015 debut as Lucy in The Sparticle Mystery. The actress is known for her performances in series such as Curfew (2019), The Letter for the King (2020), Us (2020), The Irregulars (2022), and Doctor Who: Flux (2021)

Related Sex Education Articles:

Netflix, News, Streaming Service, TV, TV News
View all