Some feelings should be left hidden.
Heimdall prefers the latter, if only because he never tires of watching the inky blackness gradually being overwhelmed by golden waves of light, especially when Loki is watching the sunrise with him. These days, or rather nights, are few and far between of late, since Loki has been increasingly preoccupied with something that makes him less chatty and lively than of old, his eyes guarded and wary when they are not sparkling with laughter in the company of Thor, Freyr and the rest in Himingbjorg.
Occasionally Heimdall will catch Loki staring at him: formerly the trickster would grinningly answer that he had been attracted to the radiant face of the White God or some such glib nonsense, when asked what he was looking at; now, Loki merely smiles and turns away, though once he murmurs that he had wanted to memorise Heimdall's features before leaving on his next sojourn in Midgard. Somehow this makes Heimdall uneasy, though he remarks cheerfully enough on the touching sentiment. Loki's absences on Odin's request, or his own whims, are common and frequently protracted, but he eventually returns to Heimdall. The hall at the gates of Bifrost is, after all, the most convenient of all the residences in Asgard, and its master arguably the least demanding of Loki as a tenant.
Odin holds Loki in conference on his arrival in Asgard for a longer time than usual, and Loki's mood is correspondingly darker than Heimdall has seen since that day when his mouth was sewn shut. This evening it is as if Loki's lips are sealed again: he sits at the table in complete and uncharacteristic silence, resisting Heimdall's cautious attempts to draw him out. He has heard rumours that Loki's monstrous offspring with the witch-giantess have been disposed of, and Angrboda herself has vanished without a trace; Heimdall had not been present at the binding of Fenrir, or the banishing of Midgardsomr and Hel, and he judges it best not to inquire further of matters in which he was not invited to participate.
When Loki finally looks up from his cups, his eyes are red in the firelight, and he pushes wearily past Heimdall into the room without a word.
Loki is usually restless in bed, tossing and muttering in his dreams, kicking the carefully-placed covers off, though on winter nights he prefers the warmth of his companion, his thin fingers catching Heimdall in a vice-like grip so that it is doubtful that he is really asleep. Tonight, however, he lies silently, breathing deeply and evenly, and does not stir when Heimdall sits down next to him. Moonlight softens the angular planes of his face, making him look younger, almost childlike. Heimdall lingers a little longer than he should, gently tracing the line of the smooth cheek with his finger, knowing that Loki will be unable to return the caress.
Unsurprisingly, the room is empty when Heimdall returns.
Time passes as it did before Loki came, the watching and waiting filling his empty days and nights, and Heimdall is not the only one who feels that Asgard is further dimmed and diminished by Loki's unaccountable disappearance, following so soon on the loss of Baldr.
Loki next appears to him through a red haze, shock and pain forcing him to his knees as he recognizes his assailant; he wipes futilely at the blood pouring from his empty eye socket, trying to focus on the words Loki's lips are forming through the throbbing agony in his head, and Loki's sad eyes are the last thing he sees before black oblivion overwhelms him.
He knows that he would never have been Odin's first choice to eliminate Loki, though Thor's failure was foreseeable - after spending so much time with Loki, the Thunderer would naturally have been susceptible to the trickster's blandishments. It is fitting that he should be the next one to be sent to Midgard, and unlike his brother, there is no reason for him to spare Loki. There is an unfathomable look in Odin's eye when Heimdall proposes that he take on a child's form so as to make it easier for him to get close to Loki and meet him on his own ground, and he thinks he hears amusement in the Allfather's voice when his request is approved.
This last night in Asgard is unusually clear, but no stars are visible; only the full moon shines brightly overhead. Heimdall stands alone with his thoughts on the bridge until the first rays of the rising sun pierce the darkness, and smiles as his form fades into the light.