Vishvamitra tells Rama why Gautama's grove is empty. Indra came in Gautama's form while the sage was away; Ahalya recognised him and consented, then begged him to leave. Gautama, returning from his bath, met Indra in his own likeness, cursed him with the loss of his vigour, and cursed Ahalya to dwell there invisible for countless years, lying on ashes and living on air, until Rama should come and she honour him as a guest. Rama and Lakshmana enter, see her radiant like flame in smoke, clasp her feet and accept her hospitality; flowers rain down; Gautama returns and takes her back.
East India · Ahalya Sthan, Darbhanga district, BiharAll traditions
A temple at Ahalya-gram in Darbhanga district, in the old Mithila country, is held to mark the place of Gautama's hermitage and Ahalya's release. Other Ahalya tirthas are claimed on the Godavari and on the Narmada near Bhalod.
What is different here:
A local claim to the site; no separate narrative was found.
Shatapatha Brahmana 3.3.4.18 (the Subrahmanya call)
Pan-IndiaAll traditions
In the litany that invites Indra to the Soma pressing, the priest calls him, among other titles, 'lover of Ahalya'. The Brahmana gives no story. Eggeling's note says Ahalya is said to have been the wife of Gautama (or Kaushika) and loved by Indra, and that very little is known of the myth.
What is different here:
An epithet only: no disguise, no curse, no Rama, and no blame.
The encyclopedia article reports that the Ramayana's Uttara Kanda recasts the event so that Ahalya is deceived and blameless; that Kalidasa's Raghuvamsha is the first to make her a stone restored by the dust of Rama's feet; that the Adhyatma Ramayana and Tulsidas have her praise Rama as Vishnu; that the Brahma Purana turns her into a dry stream restored by the Gautami (Godavari); and that the Skanda Purana has Indra flee as a cat. None of these was opened in a primary translation.
What is different here:
Blame shifts from Ahalya to Indra; stone or dry river replaces the unseen penance; Rama is openly divine.
Outside many-towered Mithila a black rock stands on a high open field. The dust of Rama's feet drifts onto it and Ahalya revives; only then does Vishvamitra tell the story. Indra waited for Gautama's absence, drew the sage away and entered in his exact body. Ahalya came to know, yet could not give up what was not hers. Gautama returned like three-eyed Shiva; Indra began to slip off as a cat and was cursed with a thousand marks, which covered him at once. Ahalya was cursed to be stone, fell as a rough black rock and begged a limit: the dust of Rama's feet. The gods, led by Brahma, pleaded and the marks became a thousand eyes. Vishvamitra praises the virtue of Rama's feet.
What is different here:
She becomes a black rock; release is by the dust of Rama's feet, not by hospitality; she realises late and cannot stop; adds the cat, the thousand marks changed to eyes, and the gods' embassy; the miracle is told before the cause.
Sources: The Ramayan of Valmiki, tr. R. T. H. Griffith (1870-74); Wikipedia: Ahalya; The Satapatha-Brahmana, tr. Julius Eggeling (Sacred Books of the East 12, 41); Three Hundred Ramayanas: Five Examples and Three Thoughts on Translation, in The Collected Essays of A. K. Ramanujan (1999)