In the future, or the past, but mostly in the present day, a lone figure from a dead race travels. Protecting Earth and the universe (but mostly Earth) from alien invaders (mostly Daleks). His name is ... the Doctor.

Accompanying him are his brave companions:

Rose, who fancies him.

Martha, who also fancies him.

Donna, who doesn't fancy him.

Mickey, who fancies Rose.

And Captain Jack, who fancies all of the above, consecutively or concurrently.