"Change, my dear...and it seems not a moment too soon!"  --Colin Baker's first line as the Doctor

There is nothing more dear to a Who fan's heart than a regeneration episode.

Started back in 1966, it was an easy way to replace the very first Doctor, William Hartnell, after he wanted to leave the role due to (reportedly) pressures to make the then-aimed-at-children theme of Doctor Who into more adventurous stories and history lessons.  But replacing(as is now) the lead character on any show is tricky, especially if the show is young....which "Doctor Who" was, being only three years old.

So,  Regeneration was born.  The Doctor, still mysterious at this point in the show's timeline (though alien), was taken ill during his first confrontation with the Cybermen ("The Tenth Planet").  So, at the very end, the Cybermen defeated, the Doctor retreats to his TARDIS.  His companions follow, only to find him collapsed....and see him change into a completely new person, with a different persona but still with  that flare that was the Doctor.

This momentary solution to a simple problem blossomed into a virtual way to keep the show fresh.  No longer was the Doctor limited to time nor space nor a single actor.  As Patrick Troughton took over for William Hartnell, Jon Pertwee took over for Troughton, Tom Baker took over for Pertwee, and Peter Davison took over for Tom Baker.  And so, at the show's twentieth season, Colin Baker takes over for Peter Davison to become the sixth actor to play the Doctor, at least television series wise.

So, we begin the "Caves of Androzani," Peter Davison's last story as the Doctor.

After landing on the moon of Androzani Minor, The Doctor lands with his new companion Peri and is immediately caught up in the war between Sharak Jak and the officals of the planet of Androzani Major.  Apparently, Sharak is seeking revenge due to the officials trying to kill him and only succeeding him in trapping him in a hot mud flow, which disfigures Sharak.  Thus, the Doctor and Perl are just mere pawns as Sharak and Androzani Major battle.   However, the Doctor realizes that Androzani Minor is important to due a dangerous addictive drug that is manufactured and made there.....and unfortunately, the Doctor and Peri have been exposed to the raw, concentrated before-hand product of the drug which is poisoning them.  As the war continues on, the Doctor must obtain the cure from deep within the mines, as war comes to it's grisly end.   The Doctor and Peri escape back to the TARDIS, which the Doctor spills some of the antidote.  Giving it all to Peri, the Doctor succombs to the effects of the poison, hallucinates, and finally has a violent & explosive regeneration into his sixth persona.

To be blunt, this story is quite different from the rest of the 5th Doctor's stories.   Peter Davison played the Doctor as more as a innocent, child-of-the-universe type as opposed to the Tom Baker/Jon Pertwee type of dashing, experienced adventurer.  However, in this story, his Doctor is brought into a new light as a more mature adventurer, perhaps a slight bit of continuity of the whole of Davison's stint and the fact that NONE of his companions left on a good note with him (story-wise, they all left due to either getting sick of him or death).  Or, this could be due to the story being written by Robert Holmes, who basically shaped part of Who-dom early on, back in the late Troughton-early T. Baker years.

Plus, "Caves" seems more like a cruel joke to the Doctor as opposed to the normal situation of "Doctor helps people fight monster."  This is more like "Doctor comes, gets caught up in some shit, and dies because of it."  While interesting, it does lead to quite a bit of darkness and misery that is quite out of place with the usually more upbeat reign of the Davison Era plus the fact that the first three episodes move quite slowly.

But, it's worth it.  "The Caves of Androzani" is often referred to the last great story of Doctor Who as a whole, before the rocky and short reign of Colin Baker and the short, forgettable, and quite-nicely-forgotten era of Sylvester McCoy.  Thanks to a well-written and witty script by Holmes, combined with probably the best "Doctor Who" related acting Davison has done despite it's darkness and almost  depressiveness.

RATING:  Highest Recommendation for a Who Fan, quite a good episode for those who aren't.