Best Medicine is about to have a surprising guest star.
An original actor from Doc Martin has returned in new images from the Fox medical series, which acts as a remake of the British comedy-drama. The cast of Best Medicine is led by Josh Charles, who plays Martin Best, a medical doctor who opens up a small practice in Port Wenn, Maine. He deals with his fear of blood and befriending locals as he tries building a life there.
Now, TV Insider has released images featuring Martin Clunes, the star of Doc Martin, making a guest appearance on Best Medicine on Tuesday, March 3. He takes on the role of Dr. Robert Best, Martin’s father, who makes a surprise visit with his wife, Vanessa (Judith Ivey). However, Martin begins to suspect his father has a major medical complication. Check out the images below:
It was first announced that Clunes would be arriving on the show as Robert in October 2025, months before the series premiered. He’s described as an “abrasive” gastroenterologist, similar in composure to his son. He’s also estranged from his sister and Martin’s aunt, Sarah (Annie Potts), causing some hairs to raise upon his arrival.
Clunes previously starred in all 10 seasons of Doc Martin, which ran on ITV from 2004 to 2022. His guest appearance on Best Medicine acts not only as a fun nod to the show’s origins, but also as a way to further Martin’s story as he tries to uncover the real reason for his father’s arrival.
In addition to Martin and Robert’s family-oriented storyline, the upcoming Best Medicine episode will feature Abigail Spencer’s Louisa being made active principal during the school’s Spirit Week. Martin and Robert will also be working together on a medical case, operating on Mark (Josh Segarra), the town sheriff.
The premise of the episode promises a mixture of both comedy and drama, something that’s helped make the series popular in the few weeks it’s been airing thus far. Best Medicine became Fox’s most-streamed debut show in three years, earning 10.8 million views across multiple platforms within less than two weeks of its premiere.
Clunes’ involvement in the series ties it even more heavily to its Doc Martin origins, something that will likely make for some playful moments in the episode. But it also carries some level of seriousness, considering Martin will be trying to figure out his dad’s condition, which Best Medicine will likely handle in a perfect way.
New episodes of Best Medicine air Tuesdays at 8 p.m. ET on Fox.
Release Date
January 6, 2026
Network
FOX
Directors
Jaime Eliezer Karas, Jamie Babbit
Josh Charles
Dr. Martin Best
Abigail Spencer
Louisa Glasson