Based in the universe of his MS Paint Adventures web comic Homestuck, it will focus on a girl who is accidentally transported to the planet of Alternia—home of the troll species seen in Homestuck. It will be the first of two games, with a second, future installment featuring a male troll who was swapped onto Earth in her place.
The game was the subject of a crowdfunding campaign on Kickstarter, raising over US$2.4 million in funding. While development initially began with developers The Odd Gentlemen, it was eventually moved back in-house under What Pumpkin's own newly formed game development studio.
Act I was slated for release in Mid-2015, however this release date was delayed indefinitely.
Source: Wikipedia, "Hiveswap", available under the CC-BY-SA License.