Heartbeat is a period drama set within the North Riding of Yorkshire during the 1960s. Plots for each episode are centred around the fictional locations of Aidensfield and Ashfordly, occasionally including the real town of Whitby. Some episodes featured references to the counterculture movement of the 1960s.
The programme's title was chosen by writers to represent the series' key characters who worked as police officers and medical staff – "heart" for the medical themes featured regularly in the programme, and "beat" for a policeman's "beat" or area that he patrols. Each episode's set of storylines were inspired by those of the Constable series of books, written by Nicholas Rhea (the pen-name of former policeman Peter Walker), which were focused on a police constable in the 1960s who came to Aidensfield. Many of the characters and locations in the Constable series were used for creating the setting and plots in Heartbeat, under guidance from Rhea.
The series was originally intended as a launch platform for actor Nick Berry, following his involvement on the BBC's soap opera EastEnders. Berry and actress Niamh Cusack were the prominent main actors of the programme for its first two series. Storylines mainly focused around both their characters, as they offered aid to those around the village and beyond, though the tone of plots was portrayed with grittiness and social realism. From the third series onwards, the role of the village policeman continued to be central to the storyline, but supporting actors were redefined as the programme's main cast, with their characters elevated in presence, effectively developing Heartbeat into an ensemble drama that was themed as more cosy and comfortable compared to more modern TV police dramas. The changes were more notable by how supporting actors gained more prominence in the opening titles after being elevated into the series' main cast – up until the fifth series, both Berry and Cusack were prominently featured in the opening credits, but this changed in later series so that by the beginning of the seventh series, all actors in the main cast were given credit for their involvement.
After the fifth series, storylines became less centralized around the village constable, focusing on separate storylines that retained a set structure within episodes: one focusing on a crime solved by the village constable and his colleagues at Ashfordly police; one focused on a medical issue that the village doctor and/or nurse would treat; and a side story focused on the programme's "lovable rogue" character which mainly was designed as comic relief, but sometimes featured light-hearted plots. In addition, over-arching storylines covering several episodes or even series, provided sub-plots between main characters, allowing for character and relationship development between them, with additional characters added in over time. In time, Heartbeat saw the cast being changed throughout its broadcast history, as new characters were introduced to replace those who left the show.