The later seasons of the series follow a war between the United Federation of Planets and an expansionist empire known as the Dominion, ruled by the shapeshifting Changelings, which has already absorbed Cardassia.
The station physician Julian Bashir has inferred that the Federation's shadowy black ops agency, Section 31, infected Odo deliberately to transmit the disease to the Dominion's Founders.
In this episode, Bashir and Chief Miles O'Brien invade the mind of a dying Section 31 agent to find a cure for the disease.
Odo asks his lover, Colonel Kira Nerys, to return to her mission aiding the Cardassian rebellion against Dominion rule, rather than stay to watch him die.
Agent Sloan takes the bait, and Bashir captures him and prepares to interrogate him with a memory-scanning device to learn the cure for the Changeling disease.
Bashir and O'Brien are seemingly shot by a figure defending Sloan's secrets, and discuss their friendship before attempting to continue the search.
He criticized the episode's slow pace and its focus on the Section 31 storyline at the expense of other plot lines in the concluding story arc.