Britannicus did not venture to breathe a word to Titus of a secret which was not his own; but there was one person from whom he could have no secret, and that was the young Empress, his sister Octavia. When he could be secure that no spy was at hand, that no ear was listening at the door, that no eye was secretly watching him, he would talk to her with wonder and admiration of all that he had heard. She was no less impressed than he, and without venturing to embrace the new faith, both sister and brother found a vague source of hope and strength in what they had learnt from Pomponia. To them it was like a faint rose of dawn, seen from a dark valley, shining far off upon the summit of icy hills. And as they learnt more of what the Gospel meant, and learnt even to pour forth dim prayer into the unknown, they were able to discover, by certain signs, that not a few of the slaves in the household of Cæsar--Patrobas, Eubulus, Philologus, Tryphæna, and others--were secret Christians. The manner in which they discovered that these slaves were Christians was very simple. Pomponia, implicitly trusting the young Cæsar, had ventured to teach him the Greek Christian watchword, Ἰχθύς, ‘fish.’[27] The brother and sister found that if, in the presence of several slaves, they brought in this word in any unusual manner, a slave who was a Christian would at once, if only for a second, glance quickly up at them. When they had thus assured themselves of the religion of a few of their attendants, whom they invariably found to be the most upright and trustworthy, they would repeat the word again, in a lower voice and a more marked manner, when they passed them; and if the slave in reply murmured low the word ἰχθύδιον or _pisciculus_ (i. e. little fish), they no longer felt in doubt. The use which they made of their knowledge was absolutely innocent. Often they did not say a word more on the subject to their slaves and freedmen. Only they knew that, among the base instruments of a wicked tyranny by whom they were on every side surrounded, there was at least a presumption that these would be guilty of no treacherous or dishonourable deed.