The Federation medical trustee who supervises the transport of deadly plasma plague specimens aboard the Enterprise-D in the second-season opener The Child.
Lieutenant Commander Hester Dealt is the medical trustee of the Federation Medical Collection Station on 'aucdet IX. He appears in The Child, the first episode of the second season.
An outbreak of plasma plague in the Rachelis system requires samples of every known strain to be carried from his station to a research laboratory so that a vaccine can be developed. Dealt comes aboard to oversee the containment module that La Forge has built, and makes no secret of how lethal the cargo is.
During the voyage one strain begins to grow inexplicably, threatening to breach containment. Dealt identifies Eichner radiation as the stimulus, and its source proves to be Ian, the alien child born to Deanna Troi, who leaves the ship to end the danger.