Question: why did the girl on desperate housewives kill herself

title: Mary Alice Young
text: Felicia Tilman ( Harriet Sansom Harris ) , Martha 's sister , soon arrives on Wisteria Lane to find out what happened to her sister . While inside Paul and Mary Alice 's house , she recognizes a picture of Mary Alice and claims her to be Angela , a nurse she worked with years prior in Utah , but Paul is adamant that she is mistaken . Felicia , however , knows that Mary Alice was in fact Angela and later tells Zach that she knew him when he was a baby , and that his original name was so lovely : Dana . In the first - season finale , the mystery behind Mary Alice 's suicide is revealed in full . In March 1990 , Todd and Angela Forrest could not conceive and one night a woman named Deirdre Taylor ( Jolie Jenkins ) , a heroin addict whom Angela had treated at the rehabilitation hospital where she worked as a nurse , came to their house looking for money and offered to sell her son to them , to which they eventually agreed . When Deirdre returned to the hospital as a patient soon after and suspicion arose as to where her child was , Angela knew they had to leave town . They moved to Fairview and bought a house on Wisteria Lane , changing their names to Paul , Mary Alice and Zach Young . In 1993 , however , Deirdre came to their home , seemingly sober , demanding that she reclaim her son . After a verbal fight , Deirdre went to take her child , when Mary Alice stabbed and killed her . Zach woke up and saw the body , which led to years of his parents brushing off his memories of that night as nothing . Paul and Mary Alice dismembered Deirdre 's body , put it in a toy chest and buried it under their pool . Years later , Martha recognized Mary Alice in a group photo in Felicia 's house , leading to Felicia to tell Martha about how Angela and Todd possibly disappeared with Deirdre 's child and hopefully gave Dana a proper home . Martha then blackmailed Mary Alice and she , in desperation , committed suicide . 

Answer: answer: Todd and Angela Forrest could not conceive and one night a woman named Deirdre Taylor came to their house looking for money and offered to sell her son Dana to them.  They moved to Fairview, changing their names to Paul, Mary Alice and Zach Young.  Deirdre came to their home demanding that she reclaim her son.  After a verbal fight, Deirdre went to take her child, when Mary Alice stabbed and killed her.  Zach woke up and saw the body, which was buried under their pool.   Years later, Martha recognized Mary Alice and then blackmailed her and she, in desperation, committed suicide.