"The Alternative Factor" is rare exception to the quality rule of TOS's first season. Occasionally good acting is kill kill kill kill killed by outrageous writing and insufferably poor special effects. Enterprise finds Lazarus chasing a murderous beast and willing to lie, steal, or fall off a cliff to fight it. McCoy notices irregularities and Kirk deduces two men, good and bad. These two use their ships to fight each other, their conflict causing physical law to "wink out" in violent rips felt far away. Kirk surprises Lazarbad and accidentally "corridors" to a parallel world where he meets Lazargood. He asks Kirk's help to manhandle Lazarbad into the "corridor" where together they are trapped forever.

Spock admits "a parallel universe has been scientifically conceded," except that it's not just "a" parallel universe but many, many more! Quantum mechanics suggest certain properties of particles, like position and spin, do not exist until they are "observed" by an "observer." Before that they are a mathematical construct, a coherent superposition of all possible values. (Minds ranging from Einstein to Berman balk at the nutty QM theory but computer chips and lasers continue to work based on it.) The Many Worlds Interpretation (multiverse) introduces a conceptually simple but unusual improvement, "parallel" universes as real as the one we consider our own. This theory has been refined to withstand significant experimental challenge but prescient Trek took it for granted.

Uncontrolled hopping to the Mirror universe took enormous power. In contrast Lazarus' tiny ship easily moved macroscopic objects across multiverse slices. (Kirk "corridors" twice, shifting spatially with remarkable resolution to a hundred meters or so.) As a transporter that works between parallel worlds this "alternative warp" may be the most powerful device found in Star Trek; Lazarus claims it can "override the safety valve of eternity." (Why build the thing then? It's all about the eternity, stupid!) The "time chamber" appears in both worlds as does Lazarus, but with no signs of another Kirk or Enterprise it's reasonable the devices act together (just like their owners).

The attitude of Lazarus - noble, unnecessary sacrifice before demonstrable madness - comes to nothing in the end except maudlin melodrama. The truth is neither Lazarus could face the "reality" that another Lazarus exists, since either could simply destroy their ship before allowing their "monster" to triumph in insane self-fulfilling prophecy. Madness need not have a reason, but it might have a goal; a sense of sacrifice may have a goal, but it could very well be the wrong one.