For whatever reason the ten occupants of area 51 just don't want to get involved. They're looking for an independent contractor to take care of the attackers for them in what they've dubbed operation 'Onslaught 2'.
Area 51 is being assaulted by a literally infinite swarm of attackers, surely the most serious attack in US history. So how did the simplistically rendered boffins prepare? By hiring your services with 20 seconds to go before the start of the battle, then lying out on the roof to do some sunbathing. Fair enough, that's their lookout.
There must be a lot of money involved in a homeland defence project as big as this. Well Area 51's finest have come up with an interesting performance related remuneration package. They furnish you with an initial lump sum of, get this, $30. o_O. Then they pay you for each enemy you manage to exterminate, the amount they give increases the further you get. Whilst the amount they pay you does increase, and to be fair they pay up promptly (paypal?), they only ever give you enough so that you can just about carry on against the relentless tide of attackers. That really doesn't seem too clever, and seriously $30?! Still, these guys have got to be some of the brightest number bods on the planet so I guess I'll let it slide.
The budget might seem small for Onslaught 2, but it's ok, they've hired you for your contacts. Evidently your procurement infrastructure is so tight that not only are you able to acquire military grade weaponry for as little as $10, you can also get it delivered, installed and up and running _instantly_. Clearly they came to the right person.
It's easy to question their tactics and how they chose to go about defending their installation, but they're pretty forgiving bosses. All they ask is that you do your best. Although if (when?) you fail, that means they're all dead, so there's really no comeback. It's not clear whether you get to keep any left over money once it's all over, but I think I will anyway. What're you going to do about it dead-man?
Onslaught 2 is a top notch tower defence game, and one of the most engrossing with it's clever combo system. This really is one of the very best free online games of all time, hit the link at the top of the page to play it now. I know you'll love it as much as I do.