Written in 1917 to a Protestant, St Hilarion explains the dangers of ecumenism. The book is read here by Patrick Barnes of www.OrthodoxInfo.com It is also here in a PDF version if you would rather read the text.
Click Here to listen or read St Hilarion's Thoughts on Ecumenism:
http://www.pravoslavie.ru/english/32129.htm
Jesus said "I am the Way." He built His Church to embody "the Way". The earliest followers of Jesus were called "the Way" (Acts 9:2; 19:9,23; 22:4; 24:14,22). Jesus revealed the "True Faith" and the "True Worship" for his followers to know how to follow Him along "the Way". This Way of Jesus is experienced in fullness in the One True Church, the Holy Orthodox Church.