The fifth episode for Fallout 3, Mothership Zeta, adds a new twist to the game's post-apocalyptic survival storyline -- sending you on a mission to destroy a massive alien craft orbiting the Capitol Wasteland. What's so bad about that? This UFO's packing a powerful Death Ray. One false move and the entire Wasteland goes extra crispy.

Wait... there's another mothership?

Mothership Zeta also makes other changes that keeps Fallout's role-playing action fresh. In addition to a new story and some graphical upgrades, this expansion introduces new enemies and weapons.

The new enemies, of course, are E.T.s -- and not the friendly kind either. The aliens look like they stepped out of a 1950s sci-fi flick and range from easy to kill (aliens with gold-plated helmets) to the more difficult to kill (the Abomination, a very human looking alien with a big HP). As for weapons, there are all sorts of new otherworldly tools of destruction: a pistol called an Alien Atomizer (40 damage), the Alien Disintegrator (88 damage), a melee-based Shock Baton (29 damage) and a Drone Cannon that bounces explosive charges around corners but makes it impossible to nail enemies up close.

Like Fallout 3's previous DLC, Operation Anchorage, the way you gain health has changed from the original game. Find Healing Archways, glowing arches scattered around the environment, to recharge HP or modify them to revive your full health (this lasts only a limited time). Alien Biogels (restores 26 HP), Alien Squid Food (5 HP) and Alien Warm Food (5 HP) round out the new food-based health boosters.

Zeta keeps Fallout's trademark humor intact, with bizarre conversations between fellow abductees, Alien Captive Recordings that add an odd audio history of abductions (except for #2, which features a guy from Flatbush who isn't so happy about his alien probe -- seriously hilarious).

Despite the cool new content, Zeta still lacks the big moments that made Fallout 3 so fulfilling. A classic "find room, take down power supply, shoot aliens" formula plays out for most of the game with few deviations, save for a surprise final conflict.

Zeta is still a worthwhile trip for $10 (800 Microsoft Points). It may not be as good of a vacation as Fallout 3: Point Lookout, but there's enough here to keep RPG fans occupied a few more weekends this summer.

Micheal Mullen is the Managing Editor of AOL's GameDaily. Over the past 14 years, he has written about video games, technology and celebs for ZD Net, GameSpot News and Electronic Arts.