You cannot break a sentence across multiple paragraphs. I do not mean you should not; I mean you cannot. What you are proposing to do is to split a sentence into several lines of text, with white space between the lines. It is still one sentence, and it is still one paragraph.
That said, I suggest this:
As the clock ticks down to the finish, only time will tell {if/whether}
— Captain Bob
— Slubgob, the alien explorer
and
— Boris, the spy
can save the Earth from [certain] doom.
(I put "certain" in brackets, because if our heroes might manage to avert that doom, it isn't certain, is it? So if I were to choose another word to modify "doom", I would use impending.)
(By the way, this not a matter of punctuation, it is strictly about typesetting; as such, it really doesn't belong on this SE.)