There are two 30 minute episodes included with both Trust and Betrayal, telling the story of a master assassin during civil war in Japan. This is a prequel to the much more light hearted series known as Rurouni Kenshin.
There is a new deluxe box set that's just come out, the cheapest price for that being £35. It includes a very poor movie and the the last 2 parts of the 6 part Rurouni Kenshin OVA (Reflections), however it isn't directly connected to the first four parts and takes place after the end of the 75 episode TV series.
If you're one of those old guys who think animated stuff is only for kids, watch this. Trust and Betrayal aren't at ranked number 1 on the AnimeNfo top 200 or nothing.