Star Trek: Enterprise (2001-2005) was the first series since the original series that ran for less than 7 seasons. By the start of season 4, the producers learnt that there would never be a 5th season, and they had to make due with what they could in the remaining season. It's a good series, and I recommend it. The first season is awesome. Season two is a bit more dull, but it returns strongly at the end of season two and the continuation of season three. Season four is the best. Not much more to say, really.