As a Star Trek fan who is in it for the characters and relationships above any other aspect, I have observed that throughout DS9, Odo really only had five relationships that were truly important. (Which I suppose is average, if not above average, for most characters in DS9.)
They ran the whole basic dramatic gamut. One, of course, was Odo/Kira, with Odo, for a long time, as sufferer of unrequited love. Another was Odo/Lwaxana: another unrequited love story, with Odo this time as object. Then of course there was the "best of enemies" Odo/Quark dynamic. And Odo/Female Changeling, a mixture of mother/son and temptress/prey.
Perhaps the most complex and controversial is Odo/Dr. Mora. Mora, of course, is the Bajoran scientist who discovered and studied Odo during the Occupation. He was first mentioned in "The Forsaken", when Odo told Lwaxana that he modeled his hairstyle on Mora's (though Mora was not named at that point). Mora was finally seen in "The Alternate", and again in the fifth season, in "The Begotten". The portrayal of Mora has led to a division among the Odo fans I know. What is the nature of this relationship? Is it father and son? Is it (former) tormentor and victim? Is it both?
The plot of "The Alternate" is as follows: Dr. Mora arrives on the station, much to Odo's annoyance, with news of the discovery of DNA resembling Odo's in the Gamma Quadrant. Since this could be the key to his still-unknown origins, Odo accompanies Mora (along with Dax and another scientist) to the planet in question. There, they find a pillar with mysterious writing, and a continuously mutating mosslike life form which seems to be the source of the DNA readings. Both are taken back to the station, but not before an earthquake releases a volcanic gas that overcomes the humanoids; Odo seems quite unaffected.
That night, the station's science lab is attacked and the life form sample stolen. It is later found dead by O'Brien in a conduit. The next night, there is another attack in the infirmary; where Mora is still recuperating; Bashir sees a shadowy, shapeshifting form which disappears into a vent. Mora finally recovers fully enough to help in the investigation. When he studies the DNA of some residue left behind by the "creature", he recognizes it as belonging to Odo.
Apparently Odo was affected by the gas after all: it caused a kind of split personality, in which, unknown to him, he goes on these rampages during his regeneration periods. Mora confronts him, hoping to use this affliction to get Odo to come back to the lab, but Odo's fear and rage at the prospect cause him to become the creature before Mora's eyes. There is subsequently a trap laid and a cure, after which Odo and Mora are reconciled.
"The Alternate" is one of DS9's "forgotten episodes" --meaning that I have seen very little discussion of it, except by Odo fans. This is understandable; it's actually pretty forgettable if you're not an Odo fan. A fairly pedestrian combination of inspirations from The Original Series' "The Enemy Within" and your basic generic monster movies. There's nothing about it that seems particularly fresh or different. It's a timeslot-filler, albeit one with excellent performances by James Sloyan (as Mora) and, of course, by RenÚ. But since I am an Odo fan, this episode is interesting to me, because, naturally, of the relationship between Odo and Mora.
Plainly, Mora is meant by the writers to be seen by viewers as Odo's father figure. After all, there had to be some way that a lump of goo in a laboratory got to wind up as security chief on a space station. Odo is an intelligent being with a broad range of knowledge. This means that someone had to have taught him. Odo is also a compassionate being, capable not only of small random acts of kindness but of an all-consuming love. This means that someone had to have cared for him. In canon, we were never presented with anyone who could have been that person--no one except for Mora.
Yet we know that, in the course of finding out what this strange liquid creature was, Mora conducted many experiments on Odo. We also know, thanks to "The Begotten", that Odo remembers these experiments with deep bitterness. We know that even after Mora knew that Odo was sentient, he condoned his exploitation as a party novelty, causing Odo much humiliation, which led to the emotional repression that caused him so much pain later in his life. Of course, the Cardassians most likely gave Mora no more choice in the matter than Odo had, but it's doubtful that that made much difference to Odo's perceptions at the time. In "The Alternate" and "The Begotten", we see for ourselves that Mora can be arrogant, insensitive, and manipulative, though in a smiling, affable way that comes across as warm and charming (to everyone but Odo). He is a skillful practitioner of the art of the guilt trip.
But what happens, in both episodes? Mora comes to the station, and manages to maneuver Odo into doing something he (Mora) wants. Odo's resentment builds until it explodes in some fashion. Then, at the end, there's a concession, not only on Odo's side, but on Mora's. Mora seems to realize what he's done, and is genuinely remorseful. He actually makes a gesture of affection toward Odo, and Odo returns it (the hand-holding in "The Alternate", the hug in "The Begotten"). Everything's fine again. For how long? Who knows? But the warm fuzzy glow is nice while it lasts.
There's definitely a familiar chord there. Some real parent/child relationships are very much like that, with that same confused love and rage on both sides. And I have to admit that I can't help liking Mora, despite all the things I know he did to my favorite character. After all, Odo forgives him. The fact that he's capable of doing so says at least something positive for Mora, as well as for Odo's generosity of spirit.
All of which reminds me of why I love Odo, and why I love DS9.