Cloak and Dagger are a fighting team that showed up in various Marvel Comics, including sometimes their own, during the 1980s.
During the 1980's, many Marvel titles and plots eschewed sci-fi and cosmic plots to focus on urban and street themes. Cloak and Dagger, along with such established heroes as Spider-Man and Daredevil helped fill that niche.
Cloak and Dagger were a pair of superheroes who symbolized light and dark, down to the fact that Cloak (Tyrone Johnson) was a black man while Dagger (Tandy Bowen) was a white woman. Both were teenagers, and sometimes had trouble with their weird powers.
The origin of Cloak and Dagger deals with how Tandy, a spoiled unhappy rich girl, and Cloak, a poor black man with a stutter from the South Boston ghetto both ran away home and ran into each other on the streets of New York City. Right after meeting, they were hauled away to an abandoned warehouse where they were shot up with a mixture of experimental drugs. They managed to escape, but found that the drugs had mutated them into a weird form. Dagger now brimmed over with light, which she could project at people, while Cloak turned into an intangible dark figure who could suck people into the darkness of his body, teleporting them and leaving them partly insane.
This being a Marvel Comic, the two set out to be tough yet just vigilantes who prowled the streets of New York getting in gritty noir situations, or at least what passed for gritty noir in a mainstream comic. They would occasionally meet up with Marvel's powerhouse heroes, such as The Avengers, but mostly kept to themselves in the ghetto of the city.
The dramatic tension with Cloak and Dagger, as far as dramatic tension goes in comics, centered around the fact that while they were in many ways innocent teenagers, they also were somewhat frightening vigilantes, especially in the case of Cloak, whose powers and appearence were somewhat monstrous.
Cloak later had problems controlling the darkness inside his cloak, and to stop it from overpowering him, Dagger absorbed it all into herself, turning Cloak back into his relativly normal self, and giving herself the powers of both of them.
While researching this node, I read that there is a plan to make a Cloak and Dagger movie, despite the fact that the book was, even in its prime, never very popular, and usually not able to sustain a regular series. I think this would make an interesting movie nonetheless.