Arc Games announces Star Trek Online: Agents of Yesterday, a third expansion coming to the Trekkie MMORPG (thanks Perrin42). Word is this will allow players to create a new captain, and will include the participation of Walter Koenig, reprising his role of Chekov, and James Doohan's son Chris. They say this will launch this summer, and provide a look in a new trailer. Here's more from the announcement:

Agents of Yesterday will allow players to create a new captain in Star Trek: The Original Series era and will set them on an adventure featuring classic story lines, locations, celebrities, and era-appropriate starships. In 2270, the year following the third season of the original series, the player will adventure with Walter Koenig, reprising his role of Chekov, and Chris Doohan, filling in for his father as Scotty. There is a new threat to the security of the Federation, and they are invading with hopes of overwhelming the past to destroy our future.

In addition to the ability to create a brand new Star Trek: The Original Series Starfleet captain, we will be introducing a new episode arc for players of every faction, the Temporal Initiative Resistance Reputation, a Temporal Operative Primary Specialization along with brand new Bridge Officer powers. Players who create their captains during the first six weeks of launch will also be able to participate in the new Temporal Agent Recruitment system for bonus personal and account-wide rewards, a new iteration of the popular Delta Recruitment system that released a year ago. This release is packed with content to keep you engaged in the classic Star Trek: The Original Series era - and beyond.