 Tessa is MacLeod 's mortal companion and bears the consequences of his immortality . These include her aging while he does not , the impossibility of having children together and the dangers of MacLeod 's involvement in the Game , an ongoing battle in which all Immortals must behead each other until a single victor remains . Fully aware of this situation , Tessa stays with MacLeod , demonstrating her courage , understanding , generosity and compassion . 
