One of Britain’s Best Police Dramas Is Finally Back — With a 100%-Rated Previous Season and Its Biggest Belfast Threat Yet

The wait is over for fans of one of Britain’s most acclaimed police dramas.

After a third season that earned a perfect 100% critics’ score on Rotten Tomatoes, Blue Lights has officially returned with Season 4 — bringing Grace, Annie and Tommy back to the streets of Belfast for what promises to be their most dangerous chapter yet.

All episodes of the new season arrived as a box set on BBC iPlayer on September 29, while the opening episode also airs on BBC One.

And this time, the officers aren’t inexperienced recruits trying to survive their first months on the job.

Three years in, they’re being pushed to their limits.

From Rookie Officers to One of Belfast’s Toughest Units

Created by Declan Lawn and Adam Patterson, Blue Lights first arrived in March 2023 and follows officers working out of the fictional Blackthorn police station in Belfast.

At the heart of the drama are three initially inexperienced constables: Grace Ellis, played by Sian Brooke, Annie Conlon, played by Katherine Devlin, and Tommy Foster, played by Nathan Braniff.

The series combines frontline policing with the complicated personal and family relationships its characters must maintain away from the job.

Audiences responded strongly.

According to the source, each of the first two seasons attracted more than four million viewers per episode, leading the BBC to commission both Seasons 3 and 4.

Season 3 Took the Crime Beyond the Streets

The third season expanded the world surrounding the Blackthorn officers.

Rather than focusing only on criminals operating directly on Belfast’s streets, the story explored the people helping organized crime function behind the scenes.

That included white-collar facilitators such as lawyers and accountants, widening the officers’ understanding of the criminal networks surrounding them.

The season also received exceptional reviews.

Season 3 holds a reported 100% critical rating and 93% audience score on Rotten Tomatoes, setting an extremely high benchmark for the next chapter.

Now the consequences of everything Grace, Annie and Tommy have experienced are following them into Season 4.

They Aren’t Rookies Anymore

Three years into their careers as response officers, the central trio has changed dramatically.

They’ve already experienced pain, grief and guilt, and the new season finds them operating close to breaking point.

According to the official synopsis, Grace, Tommy and Annie face a new threat on Belfast’s streets that police are struggling to control.

But the danger outside Blackthorn isn’t their only problem.

An unresolved piece of the past is about to resurface.

An Old Murder Case Threatens to Tear Everything Apart

The murder trial of Gerry Cliff becomes a major part of Season 4.

Rather than simply bringing closure, the proceedings expose what is described as a dangerous, long-buried secret.

Its consequences spread in two directions.

The revelation threatens to create chaos within the police while simultaneously destabilizing Belfast’s criminal underworld.

That puts the officers in an increasingly difficult position as they confront questions about their own futures.

The official synopsis frames their greatest challenge not simply as another criminal organization or dangerous suspect.

It’s the truth.

Grace, Annie and Tommy Face Their Biggest Decisions Yet

Part of Blue Lights’ appeal has always come from balancing police work with the emotional consequences of doing it.

Season 4 appears ready to push that tension further.

Grace, Annie and Tommy have survived the transformation from inexperienced recruits into seasoned officers, but experience hasn’t necessarily made their lives easier.

Instead, they’ve accumulated scars, responsibilities and relationships that make every decision more complicated.

With the Gerry Cliff trial threatening both law enforcement and the criminal world surrounding it, their professional and personal choices could carry consequences far beyond a single investigation.

For viewers who have followed them from their uncertain first days at Blackthorn, the new season represents another significant step in their evolution.

After a third season with a perfect Rotten Tomatoes critics’ score, Blue Lights is back — and Grace, Annie and Tommy are no longer learning how to survive Belfast’s streets. They’re about to discover whether they can survive the truth buried underneath them.

Blue Lights Season 4 is available as a box set on BBC iPlayer, with previous seasons also available to stream on BritBox.