Who wrote the script for "Haven", and what is "Haven" about?

If you are referring to the TV series, it is loosely based on Stephen King's novella, The Colorado Kid. Here is a description of the series:

"FBI Agent Audrey Parker arrives in Haven, Maine, on what she believes is a routine assignment. But the longer she stays, the more curious she becomes -- about the townspeople, who seem to be beset by a range of supernatural afflictions; about the town itself, which contains many secrets; and about her own surprising connection to this strange place."

https://en.wikipedia.org/wiki/Haven_(TV_series)

https://www.imdb.com/title/tt1519931/

"Haven" is the eleventh episode of the first season of "Star Trek: The Next Generation". The episode features the first appearance of the character Lwaxana Troi, who summons her daughter, Counsellor Deanna Troi of the starship Enterprise, to the eponymous planet of the episode's title to take part in an arranged marriage. The episode was developed from a story idea by screenwriter Lan O'Kun. The idea as originally submitted was felt to be of significantly poor quality, but was turned over to story editor Tracy Tormé, who altered the tone of the script into something more comedic. Although much of the comedic tone in Tormé's script ended up being excised, leading to Tormé declaring unhappiness with the final episode, his work was such that he was hired as the show's executive story editor, remaining in this position for the remainder of the first season.

https://en.wikipedia.org/wiki/Haven_(Star_Trek:_The_Next_Generation)

https://www.imdb.com/title/tt0708725/

"Haven" can also refer to a 2004 feature film set on the Cayman Islands. It was written and directed by native Caymanian Frank E. Flowers and starred Orlando Bloom, Zoe Saldaña and Bill Paxton.

In the film unconnected lives intersect and result in a violent chain of events that turns tranquility into chaos - a US money launderer and his daughter, a lawyer, a young fisherman in love with a rich man's daughter, other high school students, a crime gang etc.

https://en.wikipedia.org/wiki/Haven_(film)

The link to IMDb is missing, sorry.

www.imdb.com/title/tt0386504/