The great epic "Ramayana" tells about Dharma, which is the substratum for happy living. Lord Rama and Mother Sita lived an ideal life and showed us the path of virtue and wisdom. If we keep on singing Lord Rama's glory, our minds will be purified. If we read Lord Rama's stories we will be inspired to live an honest life.
Mother Sita was kept in Asokavitika in Lanka and she was full of sarrow due to Lord Rama's separation. Sri Hanumanji came to Lanka and found Mother Sita. Later Lord Rama came to Lanka with his military forces and killed Ravana and got Mother Sita back. This in Brief is Ramayana in Lanka.
In Sri Lanka, Lankini the female she - demon and Vibhishana became devotees of Lord Rama. Lord Rama had devotees even in Lanka the land of his enemy. The Glory of Rama is a wonderful thing.