The last of the wheat and corn was harvested with scythes in the fields around Road in September. At the beginning of the month two petitions were sent to the Home Secretary – one organised by the Bath Express, one by the Somerset and Wilts Journal – asking for a special commission to investigate the Road murder. Sir George Cornewall Lewis, the Home Secretary, turned down these pleas, but at the suggestion of the Wiltshire magistrates he quietly appointed E.F. Slack, a Bath solicitor, to conduct an investigation. The source of Slack's authority was at first unclear, and William Dunn, acting for the Kents, expressed the family's reluctance to cooperate: 'for aught we know you may be acting under the instructions of the detective officer whose former proceedings in this case have been condemned by the almost universal voice of the country'. Eventually, Slack divulged that he was working for the government. The Bath Express, among others, was disparaging about the way Lord Palmerston's Liberal administration was handling the inquiry – the paper described Cornewall Lewis as timid, terrified of criticism, and absurdly secretive.
Slack talked to everyone involved with the case. He conducted private interviews over three weeks, in his office in Bath, in a pub in Beckington and in the drawing room of Road Hill House. At one point he learnt that a small plot of land in the grounds was known as 'Miss Constance's garden', and ordered that it be dug up. Nothing of significance was found. He tried to interview the five-year-old Mary Amelia Kent, but was thwarted by Dunn, who argued that his client's daughter was too young to be examined. Dunn later described how it had been established that she was unfit to testify: when asked how old she was, she incorrectly gave her age as four; she claimed her family went to church daily, though Christ Church was not open every day; and she could not spell her murdered brother Saville's name: 'Please, sir, I have not been taught that.'
On Monday, 24 September, Slack closed his inquiry, letting it be known that he believed Constance Kent quite innocent. Her purse, he said, had been discovered behind her chest of drawers, which supported her claim to have been searching for it when she asked Sarah Cox to look through the laundry baskets on the day of the inquest. At Slack's behest, Superintendent Wolfe arrested Elizabeth Gough in Isleworth.
On Monday, 1 October, Gough was brought before the magistrates at the Trowbridge police court. The Kent family arrived in a fly, 'and were fortunate to get in unobserved', said the Bristol Daily Post, 'and therefore without any unpleasant demonstration from those congregated in the locality'.
In court, Gough sat with her hands drawn up to her throat, as if in prayer or protection. She was even 'thinner and more pale and careworn', according to the Bristol Daily Post, and watched the proceedings of the next four days with 'feverish anxiety'.
Gough's prosecutor argued that no one could have abducted and killed Saville alone, and that if two people had done it, one was surely the nurse. He questioned the credibility of Gough's statements so far. Why would she assume Saville's mother had taken him that morning, since she was too pregnant to lift him? Why did she change her story about the time at which she noticed the loss of the blanket? How could she see whether Saville was in his cot without getting out of her bed?
When Samuel Kent took the stand he was asked why he had been reluctant to let anyone draw up a plan of his house, why he had ridden to Trowbridge on the morning his son disappeared, and why he had locked the two policemen in the kitchen that night. He expressed confusion about the events of the day of Saville's death: 'my mind is so disturbed that there are many things I am not so clear about as I could wish'. On the question of the constables' incarceration in the kitchen, he said, 'I bolted the door that the house might appear as usual, and that no one might know there was a policeman in the house.' Foley was asked about the incident. 'I did not desire him to lock them up,' said the Superintendent. 'I was very much surprised when I heard of it.' He tried to make light of his part in the botched job with a weak, but pointed joke: 'They were, I understood, to have the whole range of the house, but they only had the kitchen range.' Samuel wept when he recounted the moment at which Peacock had told him of his son's murder.
The testimony of the rest of the Kent family was distinguished by its blandness. Mary Kent reluctantly lifted her thick black mourning veil to give her evidence; she was barely audible, and was repeatedly requested to speak up. She said of Gough: 'This girl, to the best of my belief, was particularly kind to the child, and seemed very fond of him; he was very fond of her; I can't tell whether she was much distressed that morning; I was too much occupied with my own and my husband's feelings . . . The boy was a nice little, playful, good-tempered, chatty boy, and a general favourite; I don't know of any one who entertained revengeful feelings against my family or little boy.'
Mary Ann Kent said, 'The poor little one who was murdered was my brother.' Elizabeth said, 'I am . . . the sister of the poor little fellow who was murdered.' They divulged little else beyond the times at which they had gone to bed and awoken on the night of his death.
Constance, with a veil pulled over her face, testified that Saville 'was a merry, good-tempered lad, fond of romping. I was accustomed to play with him often. I had played with him that day. He appeared to be fond of me, and I was fond of him.' William, who had been summoned from his boarding school near Gloucester, answered the questions put to him with 'Yes, sir' and 'No, sir' – 'not a strong-looking youth', remarked the Bristol Daily Post. Elizabeth brought the five-year-old Mary Amelia into the courtroom to testify, but an argument broke out about whether she was fit to do so: did she know her catechism or understand an oath? Eventually she was removed from the court without being examined.
The servants of Road Hill House made ingenious – and touching – attempts to help Gough by showing that a stranger might have taken Saville. On Tuesday, Sarah Kerslake, the cook, told the court that she and Sarah Cox, the maid, had experimented on the drawing-room window that very morning. They wanted to establish whether someone standing outside the house could have pulled it down to within six inches of the ground, the condition in which it had been found on the day Saville died. 'People said it could not be done from the outside, and Cox and I were determined to see whether it could or not; we found that it could be done from the outside quite easy.' The chairman of the magistrates pointed out that, even if they were right, it remained impossible that the window had been opened from the outside in the first place.
When Sarah Cox was called the next day, she told the court that she had followed up this experiment by trying to adjust the shutters of the drawing-room window from outside the house, but had been unsuccessful because the wind had been too strong. Superintendent Wolfe took issue with her: he had witnessed the exercise, he said, and the wind had nothing to do with its failure. He added that he had conducted his own experiment that morning, and it had confirmed his theory that Gough could not have detected the child's loss as she described. In Wolfe's experiment Mrs Kent took Eveline, now twenty-three months old, into the nursery, and Elizabeth Kent tucked her into Saville's crib. PC Dallimore's wife Eliza, who was a similar size to Gough, then knelt on the nursemaid's bed to test whether she could see the child. She reported that she could see only a small portion of pillow.