"The battle rages at the very threshold of our laboratory now. Those of us working to the last know that these few final hours have been dearly purchased, yet our concentration has not waned. We cannot hope to save ourselves but we can hope that one last insight, one last revelation before we take our dying breaths, may prevent this terrible day from happening again."
— Ferrel's last journal entry
Sheppard's team as been in negotiation with the comparatively technologically advanced people of the planet Hoff. The Hoffans have painstakingly preserved their learning through each Wraith culling, and now believe they are on the brink of a defensive breakthrough. The "weapon" is a drug that they hope will prevent the Wraith from draining the life of those inoculated. A previous team, lead by a Dr. Ferrel, had been on the verge of breakthrough during the last Wraith culling 150 years ago, and Hoffan scientists have finally succeeded in replicating (and perhaps improving on) his work.
The research looks promising, so Dr. Beckett is called in, along with more advanced equipment (like microscopes). He and the Hoffan chief scientist Perna are able to develop the drug to a state of efficacy against Wraith cells in laboratory conditions. The next step, of course, is to test it against a living Wraith. Happily, Atlantis happens to have one, Steve the Wraith, captured in an earlier episode.
The Hoffans are also able to provide a terminally ill man more than happy to donate himself to the cause, no matter the risk. Although such an experiment raises severe bio-ethical issues, both on the side of Steve (vis a vis the Geneva Conventions) and on the side of the Hoffan volunteer (vis a vis Dr. Beckett's Hypocratic Oath), they eventually decide to go ahead. Perna shoots the volunteer full of the drug and they toss him into the cell with Steve.
The drug works perfectly - Steve is unable to feed and there is much general rejoicing (apart from Steve, of course). Against Dr. Beckett's objections, the Hoffans immediately begin to distribute the drug to their entire population. Rejoicing turns to alarm, however, when within 24 hours both Steve and the Hoffan are dead. Soon more Hoffans are dropping, and Sheppard asks them to stop the inoculations. It turns out that the drug, while effective, kills 50% of the people who take it. To the Hoffans, however, this is an acceptable sacrifice for the benefit gained, and even knowing this statistic, 96% of the population remains in favor of general distribution, although the leader earlier refused to specify how the referendum question was worded. Despite Sheppard's warning that the drug's poisonous qualities will invite retaliation rather than apathy from the Wraith, he is unable to convince the Hoffans to stop the inoculations. The team leaves in horrified disgust, speculating that if the ever return, no one will be left alive.