S4, E102: Mars, 2059. Bowie Base One. Last recorded message: 'Don't drink the water. Don't even touch it. Not one drop'. The Doctor faces one of his darkest and most action-packed adventures yet as he arrives on Mars to find a terrifying alien virus sweeping through the colony. But he knows the events of 2059 hold an important place in history and getting involved will mean taking the law of time into his own hands. Has he gone too far?