It's May Day and the town waits excitedly for this year's pagan parade to begin. Local teenager and dark horse, Linus Newcombe, watches woefully as the love of his life, Caitlin Sutton, snogs a rival. Meanwhile, on the other side of town, Caitlin's twin and the beautiful young May Queen Hattie Sutton, catches Linus's dad Everett's eye as she passes him on her bicycle. As Hattie travels her fateful journey to appear as the town's symbol of new life, she passes various other residents, too - One is Fiona Hill and ex-copper, now housewife, who struggles to get her three kids down to the festivities, while her husband, PC Alan Hill, oversees proceedings at the parade. Meanwhile, wealthy community figure and property developer, Malcolm, smokes a cigarette, waiting for his nagging wife Gail to leave the house, is that malice in his eyes as Hattie cycles past? Wannabe local hero Steve Docker makes himself useful with traffic signs, while his more spiritual brother Seth dances a jig disguised as a 'Green Man'. Little do most of these people know that they will be the last people to have seen Hattie alive. One of them is her killer.

A worried Gail calls in support from her son, James, when Malcolm fails to surface after the night-search for Hattie. She leaves James searching Malcolm’s private office for clues as she joins the W.I.’s tea-making efforts for the day’s searches in the woods, in an effort to keep up appearances. But when Gail gets home, James has got some chilling news. The searches are enthusiastically led by Steve to further ingratiate himself to the family of Hattie, as well as cover his own worries about his brother. Steve almost misses the kick off-though when he gets held up at Seth’s flat. It’s the first time he’s ever visited and he’s shocked when he finds what Seth’s been storing there. When the police call on Linus, their routine questioning leaves him with food for thought. In an effort to try and find out more about his dad, he starts doing some investigating of his own, leading him somewhere that might connect Everett and Hattie. Alan and Fiona disagree over her desire to help with the unofficial searches - is it just a desperate attempt to feel useful? Fiona can’t help feeling that she’s bound to find something. A discovery later, however, isn’t quite what she had in mind. Meanwhile, Everett is one of the only men to resist the searches and, as Steve lands himself in trouble with the police in the woods, away from the searches, Seth makes his own horrible discovery.

Gail struggles to deal with devastating new. With the public spotlight of suspicion now firmly on Malcolm, Gail and James become the focus of family and town residents seeking vengeance with horrible repercussions. But there’s still no sign of Hattie, dead or alive. Fiona can’t help once again putting her copper training to use when she spots Everett with a suspicious-looking acquaintance. Meanwhile, Alan must face an intimidating day of interviews regarding the accusations of assault leveled against him on the evening of May Day. Above all, the Hills must cope with an increasingly paranoid Charlotte. Meanwhile, Steve’s relieved that Malcolm is firmly top of the suspects’ list for now. He winds up Hattie’s parents suspicions of Malcolm and bends their ear about calling in help from his estranged ex, Angie, with the hope of seeing her again. Later, he calls in the help of a mental health crisis team to try and deal with Seth’s increasingly erratic behavior. However, things twist unexpectedly when Seth turns the tables on Steve. Linus’s relationship with Caitlin develops when she confides in him about a shameful secret concerning May Day. Then, Everett stumbles across the young couple, provoking an alarming reaction.

The Hill household’s thrown into panic when Fiona wakes to her worst nightmare, bringing things to a confrontational head between her and Alan. Alan decides to try and fix the troubled Charlotte himself, whilst Fiona makes a visit to someone that she hopes can quell her mind once and for all. Meanwhile, on the other side of town, Seth’s suspicions seem unabated as he continues to hold Steve hostage in his own home. Even more worrying are the vivid recurring visions of Hattie that plague Seth - is his mind playing tricks on him, or could these be the real deal this time? Gail’s determined to give Malcolm the send off he deserves and her lack of forgiveness drives a wedge between her and James. But when news arrives of a significant development, it seems that nearly everyone’s off the hook. Except for Everett, whom Linus suspects more than ever - where exactly is he? It would seem in a very dark place. Back at work on the beat, Alan makes a shocking find that changes everything. A devastated Caitlin inspires Linus to embark on a mission to expose the truth, whatever the consequences. But he might just go too far. And when Seth’s visions seem vilified, he’s driven to drastic self-sabotage, despite Steve’s warnings. As a result, Steve must use desperate measures to get closer to his son.

It’s the day of Hattie's memorial and Caitlin's plagued by a loved one's desperate efforts to give her a message - if only she could work out exactly what they were trying to tell her. Seth, too starts to feel a sense of revelation and prepares himself to publicly deliver some good news to the rest of the town. But will they thank him for it? The residents get ready for the somber gathering in their own ways. After his heart to heart with Fiona, Linus knows that he’s potentially kicked off something unstoppable and goes to Everett - using force as a last attempt to extract honest answers from his father. But will Linus be able to cope with what he learns? Later, when Everett gets a visit from old flame Fiona, it’s clear that things were never quite what they seemed. Steve is still desperate to win back his family and, when Richard asks Steve for help, Steve’s driven to commit the ultimate betrayal. Meanwhile, Fiona and Alan help to bring order to proceedings when the memorial takes an unexpected turn. Meanwhile, Gail uses the gathering to catch up with Malcolm’s old friend and discover once and for all what Malcolm was up to on May Day. Will Gail finally get closure? Later, when Fiona reconnects with her ex-colleagues, it looks like the killer will finally be brought to justice.