Complete story — includes the ending
The team investigates mysterious happenings on board a Wraith Hive, where Todd and his crew are suffering from a disease, just to find that since Wraith ships are organic, the ship has the disease as well. It's revealed they got this disease when they tried Keller's gene therapy which did work, but left them with a weakened immune system. Todd offers a possible solution: allow them to be fed on by an iratus bug queen but Sheppard refuses. At the same time the team has to deal with feral Wraith warriors and the ship's deteriorating condition. Eventually the ship splits in half, killing all but the team and Todd, but the front half falls into the planet's atmosphere. Todd manages to land it in the ocean and everyone is rescued by Atlantis before the ship sinks. Keeping a deal he made with Todd and believing Todd could be a powerful ally, Sheppard sends Todd through the Stargate to seek his cure.
Sources and content license
Source and revision history · Adapted from Wikipedia contributors, Stargate Atlantis season 5. HTML formatting and reference markers removed. · Content license