Synopsis
This whole issue is a flashback to Thanos' remembered past.
Thanos is now a teen (15 or more). His aversion to dissecting specimens in biology class has long gone and he is now an expert and quits the class. He's outpaced all his other teachers as well.
He meets the mystery girl (who we don't yet officially know is Death) and takes her to his private lab where he goes further than his school would allow and dissects a live cave ape. The thrust of his research is to find out why he's different from the other Titanians. Of course this experiment gives him no answers and the girl suggests he's looking in the wrong place. He tries to kiss her but she pushes him away saying that he won't find the answer there either.
Later Thanos spies a pair of young lovers in the wilderness. He kidnaps them and cuts *them* up in his lab. This is the 1st Titanian murder. Everyone wonders where they've gone. The mystery girl knows but Thanos is still not satisfied.
Later Thanos is having dinner with his father Mentor. His mother Sui-San is also at the table, out of her straitjacket but still unresponsive. Grandfather Kronos, who is an ascended cosmic being, is paying a floating visit trying to convince his son that the lovers have been abducted but may still be alive for now (so he's not *that* omniscient). Mentor objects that his father knew violence and death in the Uranosian War but Titanians are completely peaceful. Kronos looks at his grandson suggesting that he suspects the truth.
Mentor hears his other son Eros having fun off-panel and tries to get him to join the family meal. He also tries in vain to get his wife to talk. (It seems this is her 1st time out of the asylum.) Thanos is left alone with his mother. Sui-San at last speaks to say "I know what you are". (Last issue we saw her try to kill her son at birth declaring him a monster, which is what got her put away.) Thanos replies that neither of them know *that*.
Later the girl watches him burying his 2 victims in the wilderness. He tells her that his investigation is a dead end. He swears never to kill again but she suggests that he enjoyed it. 2 weeks later he's burying another body and admits that he just couldn't stop. The girl assures him he's fulfilling his destiny. Again he tries to get her to kiss him and again she refuses, claiming love is not for the weak. He says he could force her to 'love' him, but she tells him he *couldn't*. And he backs down and finishes the burial.
In the final scene he's preparing to dissect another Titanian. He describes to her how he's progressed in his craft and has now killed 17 people. He claims it's the only time he doesn't feel alone because he has no-one to love and no-one who loves *him*. He's still trying to discover what made him the monster he is, and she is his last hope. And we see that his latest victim is his mother.