 However , executive producer Bill Panzer was intrigued by the idea that a mortal would want to spend their life with an Immortal , this choice having several drawbacks . MacLeod does not age , while Tessa is mortal and will age . Despite their mutual wish , they know growing old together is impossible and this uneasy thought " ... haunts them both , sometimes more than others . " As an Immortal , MacLeod is also sterile and Tessa <unk> herself to having no children . " The Sea Witch " deals with Tessa 's choice and its impact upon her life . In this episode , Tessa becomes very fond of a four @-@ year @-@ old girl and muses ; " For a while there , just for a few hours ... I felt like she was mine . I liked how it felt . But , she 's not ... I have my own life and it 's more than enough . " Panzer commented that " The Sea Witch " " ... brings forth in a very powerful way what exactly [ Tessa ] ' s giving up to be with MacLeod . " 
