The small, country town of Mullan is devastated by a flood which kills five locals. One year later, the residents are still grappling with the physical and emotional scars. Retired astronomer, Ray, has been forced to move his wife, Gwen, a formerly successful actress, into a care facility due to her worsening Alzheimer's. He's heartbroken that she no longer remembers him. Meanwhile, Gwen's old boyfriend, Max - now a bitter, lonely farmer - still pines for his lost love while struggling to hold onto his farm. A youthful stranger, Sam, blows into town with incredible energy and violent instincts and seduces the baker, Tina, the wife of a local cop, Griffo. Sam is inexplicably drawn to 12-year-old loner, Isaac, who's been blindly searching for his "missing" mother, Annie, since the flood. When Ray then discovers that his elderly dog has rejuvenated to her youth after eating something from the garden - in the same spot where Ray's young neighbour drowned - he wonders if he can use this "gift" to save Gwen.

Ray is stunned to discover that Gwen has returned home, but in her youthful body. While struggling to process this miracle, Ray informs Gwen's care home that he's now looking after his wife himself. A bewildered Max - who previously glimpsed a "rejuvenated" Gwen - searches for her, but Ray keeps her hidden. Gwen pushes Ray to take a berry from the plant, but Ray doesn't react as Gwen hoped. Gwen's old friend, Loris, suspects that Ray is having an affair with a younger woman when she catches a sight of Gwen. Meanwhile, Loris cares for her wheelchair-bound husband, Herb, who's hiding his own secret. Gwen relishes her new youth, but is soon overcome by an irrational desire which threatens to tear her and Ray apart. Sam helps Isaac in his search for Annie while he continues to wreak havoc, as Griffo starts to piece together Sam's true identity. A selfish act by Sam puts Gwen's youth - and life - in jeopardy.

With their plant dead, and after learning that the rejuvenation wears off, Ray is desperate to find another plant to keep Gwen young and cognizant. Suspecting that they grow where people drowned, Gwen uncovers a plant at Ranjeet's flood-destroyed house. However, Gwen is now consumed by her compulsion for a baby and takes the berries to Max instead. She rejuvenates Max who is overjoyed, leaving Ray devastated. Sam's desperation for another berry makes him reject Isaac who puts himself in serious danger while searching for his mother. Griffo's investigation hits a wall when his sergeant, Rhonda, won't believe his theory about Sam, as a homicide detectives arrive to search for "Tommy Brydon", Sam's older, criminal self. Sam inadvertently helps Tina face her grief and anger over her sister's death, while elderly care-home resident, Farida, returns to her rotting house to discover a miracle waiting inside.

Max is thrilled to learn that Gwen is pregnant and that their baby is growing at an incredible rate. However, Max's over-protectiveness scares Gwen and her jubilation soon turns to paranoia which makes her long for Ray. Loris is horrified that Herb has also rejuvenated, but Herb is soon overcome by a deep-seated regret which pulls him away from Loris. Meanwhile, a young Farida catches Gwen trying to steal berries from her plant and - having never stood up for herself - is now compelled to defend her "youth". Isaac recuperates from his near-fatal car accident while refusing to engage with his non-biological mother, Vivian, who wants Isaac to accept that her wife, Annie, isn't coming back. Isaac is delighted to learn that his "friend", Sam, rescued him, while Griffo tricks Isaac into revealing Sam's whereabouts. Griffo finally comes head to head with his nemesis, Sam, and comes close to exposing Sam's miraculous secret.

Isaac returns to his fort to discover that Griffo has been killed and that "Tommy" (old Sam) is tied up beside him. Sam convinces Isaac that he couldn't have killed Griffo and that he is, in fact, Sam turned old. Isaac frees Sam on the condition that he return Griffo's body to his family, even though it'll make Sam the prime suspect in Griffo's murder. After Gwen tried to escapeback to Ray, she wakes up in a remote fishing cabin where Max is now hiding her. Gwen's baby, however, is continuing to grow at an astonishing rate and she urgently needs more berries to stay young and keep her baby alive. Max heads to town to try to find a plant when he is confronted by a desperate Ray. A young Herb is compelled to track down his old war lover, Frank, much to Loris' horror. A rejuvenated Sam returns to Isaac who's found another clue to his mother's whereabouts. But will Sam finally tell Isaac the truth about where she is?

Isaac is devastated to learn the truth about his mother, Annie, and he blames Sam for keeping it from him. But Isaac then uncovers another secret about Annie which brings him closer to his surviving mum, Vivian. However, with no more berries left, Sam starts to age back. He seeks Tina's forgiveness while giving her some miraculous news, then farewells Isaac. With the police closing in, Sam is cornered by Rhonda who finally witnesses his transformation to old age. Meanwhile, Gwen is shattered after having lost her baby and reunites with Ray. Now free from her compulsion, she just wants to spend her remaining hours of youth and cognizance with him. But Ray won't give up. He's determined to locate another plant to keep her alive and finds a surprising ally in Max. The two men battle with Farida who will stop at nothing to protect what's hers. Ray is pushed to the edge of violence as he tries to hold onto the love of his life.

Three months on, a family arrive with a hidden agenda that could alter the course of human existence. Mullan’s new priest tries to rebuild faith in the town while struggling with his own demons, as a widowed Loris faces temptation. Gwen Reed lives, but is her relationship with Ray in jeopardy?

Gwen’s desperation to rejuvenate Ray drives her back to Max – but will Max pay the ultimate price? Anne’s search for the berry’s source leads her to Ray, while Luke’s true identity is revealed. Young Loris discovers her new purpose. With John desperate for a miracle, can his new acolyte, Shane, find him a berry?

Gwen’s berry-driven compulsion forces Ray to take charge, while John and Shane attempt to prove the miracle to the church. Ben tries to reproduce the berry using Gwen’s blood as Loris is overcome by her hedonistic new urges. Rhonda is startled by her own dad’s transformation.

With Gwen at breaking point, Ray and Gwen turn to John for help... but can faith in a higher power save Gwen from herself? Donnie ignores Rhonda’s warning and becomes a liability to everyone. Luke’s desire to save Anne pushes him to extreme measures, while Loris - confronted by her own behaviour - hits rock bottom.

Ray takes extreme measures to retrieve the love of his life. Luke’s selfless act reveals a surprising side-effect of the berries while Anne must decide whether to take one herself or continue with her plan to duplicate it. John retaliates against the Archbishop’s rejection while Loris attempts to reconnect with her daughter.

Ray, Anne and John’s agendas collide as they face off over the miracle. Loris puts her heart on the line with Julie. Rhonda and Donnie recalibrate their relationship.